JP2004331491A - Method of manufacturing high strength and high toughness cement-based material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a high strength and high toughness cement-based material reinforced with a fiber or a wire of a shape-memory alloy. <P>SOLUTION: A matrix (cement-based paste, mortar, or concrete) mixed with a fiber reinforcing material or a long wire reinforcing material stretched along its length direction, which is deformed by contraction at a temperature above the strength-developing temperature, is firstly cured at a high temperature to develop the strength as well as an adhesion of the fiber and then cured at a little higher temperature than the previous temperature to exercise the shape-memory property so as to introduce prestress by the deformation of the fiber reinforcing material caused by the higher temperature curing. The fiber or the wire reinforcing material is an Fe-Mn-Si-based shape-memory alloy at least containing Fe, Mn, and Si as major components and a niobium carbide in its structure. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a high-strength, high-toughness cement-based material, and more particularly, to a method for producing a high-strength, high-toughness cement-based material in which fibers or wires are reinforced with a shape memory alloy.

  Mechanical properties of cement-based materials such as concrete and mortar include low tensile strength and low toughness compared to compressive strength. When the tensile strength and toughness of the cementitious material are improved, cracks are less likely to occur, and the water resistance and durability to neutralization are improved, and the cement material can be used as a structural material for large span structures.

  As a method of improving the tensile strength, a method of introducing prestress into a material is used. In order to introduce prestress, it is necessary to tension the PC steel wire before or after the concrete is hardened. However, there are inconveniences that the above-mentioned device is required and that it takes time. Fiber reinforcement as a method of improving toughness can improve toughness without any such disadvantages.However, it cannot improve the strength of the mortar used as the matrix, which causes cracking. Sex cannot be fully desired.

  Therefore, by manufacturing the above-mentioned fibers with a shape memory alloy that recovers shape in the shrinking direction, fiber reinforcement that can also introduce prestress by recovering its shape, that is, concrete that can simultaneously provide tensile strength and toughness. There have been proposals for fiber reinforcement of cement-based materials such as cement and mortar.

  This is extracted from the public description and introduced, for example, as follows: "As shown in FIG. 10a, a fiber 1 made of a shape memory alloy is prepared. The fiber 1 has a temperature between room temperature and the temperature at the time of concrete solidification. For example, a shape memory alloy wire whose shape is contracted in the longitudinal direction is formed by cutting a shape memory alloy wire that has been drawn and is tensile deformed at room temperature. It is.

  In order to increase the entanglement with the concrete, a fiber 1 made of a shape memory alloy having a surface with macroscopic unevenness may be used.

  The fiber 1 described above is mixed into the concrete 2 and generates heat when the concrete 2 is solidified, so that the fiber 1 shrinks in the longitudinal direction, causing the concrete 2 to have a compressive internal stress. To provide reinforcement.

Hereinafter, more specific examples will be described.
An NiTi alloy wire of 55% by weight of Ni and Ti% by weight was pulled from the front side while giving a tension of about 30 kg / mm 2, and the surface was provided with irregularities by using a concavo-convex processing roll to prepare a 25 mm long fiber having an aspect ratio of 50. The fibers shrink in length by about 2% at a temperature of about 60 ° C. or higher. Using Portland cement and a magnet having a maximum dimension of 12 mm, concrete having a water cement ratio of 50% and a size of 100 × 100 × 100 mm was prepared with and without the above fibers. Using these, a load-deflection curve with a span of 500 mm was obtained, and the result was as shown in FIG. 10B. It was found that the concrete according to the present invention had a high bending toughness. (See Patent Document 1).

  Or, "the high-strength high-vibration-damping concrete material is at least one or more first shape memory alloys to which plastic elongation is imparted at a temperature equal to or lower than the transformation end point, and reverse transformation of the first shape memory alloy. At least one or more second shape memory alloys having a reverse transformation start point equal to or higher than the end point are integrated with the concrete material at a temperature equal to or lower than the transformation end point of the first shape memory alloy, and the unification is performed. The concrete material is subjected to a heat treatment at a temperature not lower than the reverse transformation end point of the first shape memory alloy and not higher than the reverse transformation start point of the second shape memory alloy.

  Such a high-strength and high-damping concrete material has a first shape memory alloy to which plastic elongation is applied at a temperature equal to or lower than the transformation end point (Ms), and a reverse transformation end point (Af) of the first shape memory alloy. ) And at least one of the second shape memory alloys having the above-mentioned reverse transformation start point (As) at the same time as the solidification temperature of the concrete-based material is not more than the transformation end point of the first shape memory alloy. keep. After the solidification and integration of this concrete material, the entire member is heated, or only the first shape memory alloy is heated positively to cause compression deformation, so that a direct current or electromagnetic induction (eddy current) effect is applied. The temperature of the first shape memory alloy is maintained at a temperature equal to or higher than the reverse transformation end point (Af) and equal to or lower than the reverse transformation (As) of the second shape memory alloy for a predetermined time by the method described above. Only the memory alloy induces reverse transformation. Then, since the first shape memory alloy attempts to return to the shape before the plastic elongation is given, it is possible to apply a compressive force to the integrated concrete material.

  On the other hand, the second shape memory alloy, which originally has a high damping property below the end point of the reverse transformation, is dispersed and integrated in the concrete material, but it maintains the low temperature phase without transformation despite the heating during the process Therefore, the vibration applied to the concrete material is attenuated when transmitting the second shape memory alloy. In this way, the second shape memory alloy provides vibration damping.

  Any known shape memory alloy may be used. For example, AgCd, AuGd, CuAlNi, AuZu, CuSn, CuZu, InTl, NiAl, TiNi (Fe, Cu), FePt, FePd, MnCu, FeNiTiCo and the like. The transformation point can be variously changed by variously changing these compositions.

As an example, a sample having the following specifications was prepared, and a (1) three-point bending test and (2) a vibration damping characteristic test were performed. As a comparative example, an ordinary concrete block was used. Regarding the shape memory alloy used and its amount, as a second shape memory alloy for vibration damping, a Ti50Ni50 (at%) powder having a particle size of 100 μm (reverse transformation start point 80 ° C.) was used in a concrete volume ratio of about 5%. . As a first shape memory alloy for compressive force loading, a TiNi wire (reverse transformation end point = 60 ° C.) subjected to a memory treatment and then added with a tensile prestrain of about 5% was used in a concrete volume ratio of about 3%. . These were obtained by arranging the first shape memory alloy wires in a material in which the second shape memory alloy and concrete were mixed in advance and solidifying them. Thereafter, heat treatment was performed at about 70 ° C. (See Patent Document 2)
Etc.
Japanese Patent Publication No. 4-27183 (column 4, FIG. 5, FIG. 6). Japanese Patent No. 3254481 (page 3).

  The above-described prior art has the following disadvantages. In other words, it is necessary to raise the curing temperature in order to sufficiently increase the compressive strength, tensile strength, and adhesion strength of the cement-based material to fibers, but to achieve a sufficiently high strength of the cement-based material, 80 ° C. or higher. This temperature is required, but there is no deficiency in this consideration. That is, the correlation between the curing temperature and the compressive strength for the high strength mortar is shown in FIG. It can be seen that a peak occurs at about 200 ° C. In addition, the heat treatment of the heat curing up to 350 ° C. is usually performed in an autoclave curing from the high temperature. However, when it is not particularly necessary to be under a steam pressure atmosphere, when the autoclave curing cannot be adopted due to the size, Other heating means such as steam spraying and electric mats are used. In order to obtain the high strength by exhibiting the characteristics of autoclave curing, it is effective to mix it with a siliceous material powder, and calcium is generated by a binding reaction between free Ca (OH) 2 generated from C3S or C2S and silica. This is for increasing the amount of silicate hydrate. Although the siliceous material mixture depends on its fineness, in the case of a paste, the optimal mixing amount in terms of compressive strength is about 40%. However, the above intensity peak can be arbitrarily adjusted within the range of 80 to 250 ° C. depending on the preparation of the matrix.

  In short, it is preferable to always add curing to the matrix in the peak region in the range of about 200 ° C., and to take care not to deteriorate the matrix having the bending strength by unnecessary unnecessary heating.

  In addition, since "tensile strength" also improves with said "compressive strength", the strength development is reasonable from this point as well.

  However, in the above-mentioned Patent Document 1, it is described that “the fiber shrinks at a temperature of about 60 ° C. or more”, and in Patent Document 2, “the first shape memory alloy for compressive force loading” Is 60 ° C., and the first shape memory alloy wire is arranged and solidified, and then heated to about 70 ° C. " At the stage, there is a problem of shape recovery. During this inconvenience, it is not only that the strength that should be given to the cement-based material is not exhibited, but also that the essential fiber adhesion strength that would be guaranteed before that is not ensured. There is also.

  Next, consideration is given to the selection of the shape memory alloy to be used. That is, a Ti-Ni based shape memory alloy is applied to military aircraft and the like in the United States as a shape memory alloy as a member that can be extremely easily replaced by pipe welding by a conventional welding method as part of energy saving. However, Ti-Ni-based shape memory alloys are very expensive and have not been used for consumer use.

  An inexpensive shape memory alloy is an Fe-Mn-Si shape memory alloy which is an iron-based shape memory alloy. This was discovered in Japan about 20 years ago and has low cost and excellent workability, machinability, and weldability, but its shape memory properties are significantly inferior to those of Ti-Ni based shape memory alloys. In order to improve this, a special heat treatment method called "Training II" has been devised, in which a process of applying a few percent deformation at room temperature, heating to around 600 ° C. and returning the shape to its original state is repeated several times. In addition, there are problems that the number of processes is large and the cost is high, and that the method cannot be applied unless the product has a certain shape. Therefore, there has been a strong demand in the industry for the development of an inexpensive iron-based shape memory alloy having shape memory characteristics comparable to Ti-Ni-based shape memory alloys.

  Among the existing shape memory alloys, the Ti-Ni-based shape memory alloy having the best shape memory characteristics has a difference between the positive transformation point (Ms) of martensitic transformation and the end temperature (Af) of reverse transformation, which are responsible for the shape memory effect. Since the difference is small, the Ms and Af temperatures cannot be set near room temperature at which work is easy, and an alloy having a composition having Ms near liquid nitrogen temperature must be used and fastening work must be performed in liquid nitrogen. Therefore, there is a decisive problem such as not only a large enforcement cost but also a significant restriction on an application place.

  However, the present applicant has discovered that a small amount of Nb and C are added to a conventional Fe-Mn-Si-based shape memory alloy to precipitate carbides (NbC) by age precipitation, so that the shape memory characteristics are significantly improved. Further, it has been clarified that by subjecting this alloy to warm working or working at room temperature before aging heat treatment, the shape memory characteristics are further remarkably improved, and the shape memory characteristics are improved.

  FIGS. 11 and 12 show how the shape memory characteristics are improved by performing warm working on the Fe—Mn—Si based shape memory alloy to which Nb and C are added before aging heat treatment.

  In addition, a specific good example of the above-mentioned "warm working before aging treatment" is a homogenizing heat treatment of an alloy after melting by adding niobium and carbon at a temperature in a range of 1000 to 1300C, and a temperature of 600C. This is a case in which after niobium rolling is performed, aging treatment is performed in the range of 400 to 1000 ° C. to precipitate niobium carbide.

  The amount of deformation required for practical use is about 4 to 5%. However, when rolling (14% and 30%) is performed as shown in FIG. As a result, a high shape recovery rate was obtained. The shape recovery force that is practically required is 200 MPa or more when the recovery strain is zero, but when rolling is performed as shown in FIG. 13, this condition far exceeds this condition. In the case of 30% rolling, even when the recovery strain is 3%, it exhibits characteristics such that a shape recovery force of 200 MPa is exhibited.

As described above, the following three points can be cited as factors that significantly improve the shape memory characteristics by performing the warm working before the aging heat treatment.
1) The size of the precipitated NbC carbide is 50 to 100 nm in the case of no processing, but is reduced by an order of magnitude to 5 to 10 nm in the case of processing.
2) When processed, precipitates are uniformly distributed. Moreover, a large elastic strain exists around the precipitate.
3) From the above 1) and 2), a state in which extremely thin plate-like martensite having a width of 3 to 5 nm is uniformly distributed is obtained as a microstructure caused by deformation.

  Although the above is the case of the Fe-28Mn-6Si-5Cr-0.53Nb-0.06C alloy, almost the same results were obtained with an alloy having good corrosion resistance in which the amount of Mn was reduced and Ni was added. Furthermore, practically advantageous characteristics are that the addition amount of Nb and C can achieve the same effect if the amount of NbC precipitated by aging is in the range of 0.5-1.5%. A short time of about 10 minutes is sufficient.

  As described above, this iron-based shape memory alloy has a feature that a large resilience is maintained even when the iron-based shape memory alloy is heated to a temperature equal to or higher than the reverse transformation end temperature (Af) and then returned to room temperature. Further, with respect to the cost including the difference in the price of the material, it is estimated that the newly developed one is at least one order of magnitude lower than the Ti-Ni type shape memory alloy, and in some cases, two orders of magnitude lower (Ti-Ni type shape memory alloy: Iron-based memory alloy = 10,000 / kg: 600 yen / kg).

  This is an important choice for cement-based materials where high costs are not acceptable. In addition, it is possible to set the positive transformation point (Ms) of the martensitic transformation and the reverse transformation end temperature (Af) of the martensitic transformation slightly higher than the temperature of the intensity peak of the matrix (100 to 350 ° C.). The setting is easy in this case.) Regarding this technique, JP-A-2001-226747, JP-A-2003-105438, and JP-A-2003-277827 are disclosed.

Further, the present applicant has not been satisfied with this and has sought further improvements.
That is, there still remains a problem in that a heat treatment at a high temperature of 600 ° C. is required, and the fact that there was difficulty in using it did not distort. Whether the shape memory characteristics cannot be exhibited even at the lowest possible temperature, and as a result of intensive studies, the shape memory characteristics are remarkable even at the room temperature, and the objectives described above are fully achieved. I can do it.
That is, the basic operation of processing a Fe-Mn-Si-based shape memory alloy to which Nb and C are added at room temperature, and then heating and aging to precipitate NbC carbide is applied. It has been found that an unexpected function and effect of exhibiting shape memory characteristics can be achieved.
This was filed in Japanese Patent Application No. 2002-367062.

In this application, an Fe-28Mn-6Si-5Cr-0.53Nb-0.06C alloy (numerical value is% by weight) was prepared by melting in Examples, and the shape memory characteristics of the obtained shape memory alloy were measured at room temperature. Shows how the shape memory property is improved by performing aging treatment by heating at a temperature in the range of 400 to 1000 ° C. for 1 minute to 2 hours after rolling.
That is, FIG. 14 is a graph showing the difference in the shape recovery ratio between the case where only aging is applied (rolling ratio 0%) and the case where 10%, 20% and 30% rolling is performed at room temperature. All the aging treatments were performed at 800 ° C. for 10 minutes. For comparison, the results of the as-annealed sample and the sample trained five times are also shown for the Fe-28Mn-6Si-5Cr alloy to which NbC was not added. The horizontal axis represents the deformation amount (%) due to tensile deformation at room temperature, and the vertical axis represents the shape recovery rate (%) when the sample is heated to 600 ° C. When heated to 400 ° C., almost the same shape recovery rate can be obtained. The test piece used in this experiment was a test piece prepared to have a thickness of 0.6 mm, a width of 1 to 4 mm, and a length (gauge length) of 15 mm.

  As can be seen from the figure, the 10% rolled sample has the same or slightly inferior shape memory recovery as the alloy trained five times without NbC. The amount of deformation required for practical use is about 4%. Even at this amount of deformation, showing a shape memory recovery rate of about 90% strongly suggests that the alloy can be used as a practical alloy. Considering that at least five trainings are required to obtain the same shape recovery ratio with a normal Fe-Mn-Si-based shape memory alloy without NbC addition, the effect can be said to be excellent. When the rolling ratio increases and reaches 20%, the shape recovery ratio is almost the same or slightly better than that in the case of no processing (only aging). Furthermore, when the rolling reduction is 30%, the shape recovery rate is worse at a place where the initial strain is larger than when only aging is performed.

  On the other hand, as shown in FIG. 15, the shape-restoring force, which is one of the important shape-memory characteristics in practical use, is significantly improved in the material subjected to aging treatment after rolling at 20% at room temperature and rolling at 30% at room temperature. I have. FIG. 15 shows the degree of improvement of the shape recovery force in comparison with the case of only aging (rolling ratio 0%) and the case of aging treatment after rolling 10% at room temperature. The recovery force when the recovery strain on the horizontal axis is zero means the stress generated when the two ends are fixed as they are after being subjected to tensile deformation at room temperature, heated to the reverse transformation temperature or higher, and then returned to room temperature again. The restoring force when the recovery strain is, for example, 2% means the generated stress measured by fixing both ends after the recovery of the strain by 2%. Testing was performed with an initial strain of 4-6% at room temperature. The same test piece as that used for obtaining the results shown in FIG. 14 was used as the test piece at that time. In FIG. 15, the recovery strain on the horizontal axis represents the degree of allowable clearance between the pipe and the fastening part (shape memory alloy) when used for the fastening part of a pipe in a practical example. Corresponding to the ratio (%) with respect to. The shape reversing force is remarkably improved at a high rolling reduction. When the rolling reduction at room temperature is 20 to 30%, a recovery force of 310 MPa at a recovery strain of 0% and a recovery force of 200 MPa at a recovery strain of 2% can be obtained. Also, it was found that even with a rolling reduction of 10%, exactly the same shape recovery force as in the case of training was obtained. That is, it is understood from the results of this figure that the shape recovery force is remarkably increased at the high rolling reduction (20%, 30%) as compared with the rolling reduction of 0% and the rolling reduction of 10%. FIG. 15 shows the shape recovery force of the solution-treated sample without NbC addition and the sample trained five times for comparison, and it is clear that the recovery force is considerably smaller than that according to the embodiment of the present invention. Do you get it.

  As described above, in the invention of this application, the processing performed prior to the aging treatment on the Fe—Mn—Si based shape memory alloy having a specific composition obtained by adding Nb and C is specified. In the range of the processing rate of the above, it has been successfully achieved for the first time by processing at room temperature.

  That is, by adopting the specific alloy, firstly, the advantage that the shape memory property can be exhibited at room temperature is enjoyed. However, the advantage that the shape memory processing operation can be completed by one training, and the great shape recovery can be achieved. It also has the advantage of being able to enjoy the amount and shape resilience, and the advantage that the shape memory processing can be performed at room temperature by applying a strain of 4 to 8%.

  The present invention, under the above circumstances, as a fiber or wire reinforcing material, by using a shape memory alloy having the property of shrinking greatly in a temperature range higher than the curing temperature at which the cement material develops sufficient strength, After the cement-based material, which has been capable of increasing the strength of the cement material by high-temperature curing to ensure sufficient adhesion with the fiber or wire in a state where the fiber or wire does not shrink, after sufficiently securing the adhesion with the fiber or wire By further increasing the temperature, the fibers or wires shrink and the introduction of prestress becomes possible, and while improving the strength of the cement-based material that is the matrix portion, the fibers or wires of the shape memory alloy fibers or wires are used. Considering that reinforcement and introduction of prestress can be performed at the same time, the practical application was made as an issue.

  The method for producing a high-strength, high-toughness cement-based material according to the present invention is directed to a niobium alloy containing niobium carbide in a Fe-Mn-Si shape memory alloy containing at least Fe, Mn, and Si as main components. Matrix made of carbide-containing shape memory alloy, mixed with fiber reinforcing material that shrinks and deforms at or above the strength development temperature of matrix (cement paste, mortar, concrete) or stretched with long reinforcing wire in the longitudinal direction The strength is formed by the initial high-temperature curing of the heat treatment for the purpose of developing the strength including the adhesion of the fiber or the wire, and the shape of the fiber or the wire reinforcing material subsequently set to a slightly higher temperature range than this. The pre-stress is introduced by deforming the fiber or the wire reinforcing material in the later-stage high-temperature curing for activating the memory characteristics.

  The above-mentioned "initial high temperature curing" and "late high temperature curing" do not need to be clearly divided, and the point is that if the fiber or wire bond strength is given, "late high temperature curing" may be activated. Absent. In this case, the development of the strength of the matrix and the recovery of the shape memory of the fiber or the wire reinforcing material are performed in parallel.

  The heating of the fiber or the wire reinforcing material may be performed by electromagnetic induction heating. In particular, when the curing temperature range of shape memory recovery of the fiber or wire reinforcing material in `` late high temperature curing '' will enter the matrix deterioration zone, heating of the fiber or wire reinforcing material hardly heats the matrix. It is good to do it with electromagnetic induction heating.

  Examples of the shape memory alloy include: Mn: 15 to 40% by weight, Si: 3 to 15% by weight, Cr: 0 to 20% by weight, Ni: 0 to 20% by weight, and Nb: 0, which are introduced in the application of the present applicant. 0.1 to 1.5% by weight, C: 0.01 to 0.2% by weight, with the remaining Fe and inevitable impurities as Cu: 3% by weight or less, Mo: 2% by weight or less, Al: 10% by weight Hereafter, it contains Co: 30% by weight or less, N: 5000 ppm or less, and the atomic ratio of Nb to C is in the range of 1.0 to 1.2 at room temperature or in the temperature range of 500 ° C to 800 ° C. After being processed at 5 to 40%, it is made of an NbC-added Fe-Mn-Si shape memory alloy obtained by precipitating NbC carbide by performing aging heat treatment in a temperature range of 400 ° C to 800 ° C for 1 minute to 2 hours. I'm glad you do.

  According to the method of the present invention described above, it is possible to increase the strength of a cement-based material, and at the same time, to introduce the effect of fiber or wire reinforcement and prestress without largely changing the method of manufacturing a normal concrete product by heat curing. And the tensile strength and toughness of the material can be improved.

In addition, a process for introducing prestress can be eliminated, so that a large-sized device such as a jack is not required, and a period for manufacturing a product can be shortened.
According to the manufacturing method of the present invention, the strength and toughness of the cement material can be increased, and the durability of the material can be improved by preventing cracks and the like. This has the advantage of increasing the degree of freedom in design. These advantages can be enjoyed at a low cost.

FIG. 1 shows an embodiment in which the fiber reinforcing material according to the first and second aspects of the present invention is mixed.
In the figure, there is a range that overlaps between the “initial high temperature curing” and the “late high temperature curing”. However, in the invention of claim 1, since the strength expression point changes depending on the type of the matrix, At the same time, the fiber reinforced material is set so that the fiber shrinks only by slightly increasing the temperature, and the parallel activation of the “initial high temperature curing” and the “late high temperature curing” in the invention of claim 2 is performed. Show. In the initial high-temperature curing, it is not necessary to maintain a constant temperature, and the strength can be developed during the temperature rise by adjusting the rate of temperature rise. As is clear from FIG. 11, when the strength exceeds the maximum strength development point, the strength starts to deteriorate, so it is necessary to pay attention to the temperature rise. An embodiment of the invention described in claim 3 is illustrated in FIG.

  In late-stage high-temperature curing, care must be taken to raise the temperature to the deterioration temperature beyond the maximum strength temperature in autoclave curing, etc., which involves matrix heating, but electromagnetic induction heating hardly heats the matrix and only fibers It is safe because it heats and introduces prestress.

  In the range where the fiber is heated to 250 ° C. or higher, the shape recovery force (shape memory characteristics appear at 100 to 300 ° C.) increases remarkably as shown in the right diagram of FIG. Prestressing is achieved.

  FIG. 3 shows the difference between the mere matrix and fiber reinforcement and the prestressed fiber reinforcement of the present invention.

  In the case of Patent Documents 1 and 2, it is understood that the strength of the matrix is insufficient, so that the level is not much different from fiber reinforcement.

  It is understood that the present invention in which the prestress is introduced under the high strength of the matrix can withstand a much larger load by a synergistic effect.

鉄系形状記憶合金には、６０．５％Ｆｅ−２８％Ｍｎ−６％Ｓｉ−５％Ｃｒ−０．５ＮｂＣを用いた。 A mortar reinforced with the following reinforcing fibers was subjected to a three-point bending test.

For the iron-based shape memory alloy, 60.5% Fe-28% Mn-6% Si-5% Cr-0.5NbC was used.

  FIG. 4 shows the relationship between the temperature of the alloy used and the shape recovery force. At 100 ° C. or lower, shape recovery hardly occurs, and a large recovery force is exhibited from 100 ° C. to 350 ° C.

  In order to make use of the characteristics of the shape memory alloy, curing was performed using a temperature pattern of high-temperature curing as shown in FIG. The initial high-temperature curing temperature is set at 90 ° C. for the purpose of increasing the strength of the mortar to achieve sufficient adhesion between the alloy fiber and the mortar, and then, the introduction of prestress using the shape recovery force of the shape memory alloy, and The temperature of the latter high-temperature curing was set to 180 ° C. in order to further increase the strength of the mortar.

  In Example 1, the mortar was strengthened at 90 ° C., and then heated to 180 ° C. in an autoclave. This corresponds to the implementation of the invention of claim 2.

  In Example 2, after increasing the strength of the mortar at 90 ° C., the mortar was heated to 180 ° C. in an autoclave, and the reinforcing fibers were further subjected to electromagnetic induction heating. This corresponds to an implementation of the invention of claim 3.

In Comparative Example 1, a stainless steel having a breaking strength substantially equal to that of the iron-based shape memory alloy was used, and the same processing as in Example 1 was performed.
In Comparative Example 2, the same treatment as in Example 1 was performed without the reinforcing fiber.

  For the preparation of the bending test specimen, Portland cement, silica fume, silica sand, water, and the like were placed in a 20 × 20 × 80 mm formwork in which four 2 × 4 × 75 mm reinforcing fibers made of an iron-based shape memory alloy or stainless steel were previously installed. A mortar comprising a high-performance water reducing agent was poured into the mortar and solidified. The mortar was maintained in an autoclave at 90 ° C. for 24 hours to increase the strength of the mortar, and the reinforcing fiber was further heated by an autoclave or heated by electromagnetic induction.

The bending test results are shown in FIG.
In the figure, the point at which the load temporarily decreases indicates the occurrence of cracks in the mortar, and the point at which the load first decreases indicates the crack generation strength.

  In Examples 1 and 2, the crack generation strength and the maximum bending strength were higher than in the case of using the stainless steel fiber of Comparative Example 1 or in Comparative Example 2 not using the fiber. It shows that the effect of pre-stress as well as the effect of fiber reinforcement appeared by using iron-based shape memory alloy as the reinforcing fiber and properly performing high-temperature curing.

  In the present embodiment, the case where the fiber is reinforced by using the long fiber is used. However, the fiber shape, the length, and the arrangement of the fiber are not limited thereto, and for example, the short fiber may be dispersed.

6 to 9 show the case of a long reinforcing wire rod in which the longitudinal direction of the matrix is stretched like a PC steel rod.
FIG. 6 shows a variation of the shape of the wire. FIG. 7 shows a variation of the stretch arrangement in the matrix. In the figure, (2) and (4) correspond to members that apply tensile force only to the lower side as horizontal members.
Although not shown, it is preferable that both ends of the wire are provided with a fixing portion.

FIG. 8 shows an introduction and a production method of the above-mentioned wire rod test piece. In the figure, “SUS304 stainless steel reinforced type” is used as a non-shrinkable material for comparison.
As described above, according to the method for producing a high-strength and high-toughness cement-based material of the present invention, it has been found that epoch-making cost reduction and strength and toughness can be simultaneously obtained.
FIG. 9 shows the bending strength test results of the above-mentioned specimen.

  According to the manufacturing method of the present invention, the strength and toughness of the cement material can be increased, and the durability of the material can be improved by preventing cracks and the like. And the degree of freedom of design increases.

FIG. 4 is an illustrative view of the method of the present invention. FIG. 4 is an illustrative view of the method of the present invention. It is a relative display graph of this invention and a prior art. 4 is a graph showing the relationship between the temperature of the alloy used in the present invention and the shape recovery force. It is a graph which shows the bending test result of this invention. It is variation explanatory drawing of the shape of the wire of this invention. It is a variation explanatory view of the stretch arrangement in the matrix of the wire rod of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram illustrating a structure of a test body of a wire rod according to the present invention and an explanatory diagram of a manufacturing method. It is a graph of a bending test of the wire rod reinforcement matrix specimen of the present invention. a is a structural illustration of fiber reinforced concrete in the prior art. b is a load deflection curve graph. It is a correlation diagram of the curing temperature of mortar and compressive strength. FIG. 4 is a correlation diagram between the deformation amount and the shape recovery rate of the alloy employed in the present invention. FIG. 4 is a correlation diagram between a recovery strain and a shape recovery force for an alloy employed in the present invention. FIG. 4 is a correlation diagram between the deformation amount and the shape recovery force of the alloy employed in the present invention. FIG. 4 is a correlation diagram between a recovery strain and a shape recovery force for an alloy employed in the present invention.

Explanation of reference numerals

1 fiber 2 concrete

Claims (4)

In a Fe-Mn-Si based shape memory alloy containing at least Fe, Mn and Si as main components, a matrix (cement-based paste, cement-based paste, niobium carbide-containing shape memory alloy whose structure contains niobium carbide) is used. (Mortar, concrete) A matrix in which a fiber reinforcing material that shrinks and deforms at a temperature equal to or higher than the strength developing temperature or a matrix in which a long reinforcing wire is stretched in the longitudinal direction is subjected to heat treatment for the purpose of developing strength including fiber adhesion. In the initial high-temperature curing, the strength is developed, and subsequently, the fiber-reinforced material is deformed in the later high-temperature curing in order to activate the shape memory characteristics of the fiber reinforcement set in a slightly higher temperature range than this. A method for producing a high-strength, high-toughness cementitious material, characterized in that prestressing is achieved by performing the method. 2. The high-temperature curing method according to claim 1, wherein the high-temperature curing is activated based on the fiber adhesion strength development of the initial high-temperature curing, and the matrix strength development and the shape memory recovery of the fiber reinforcing material are activated in parallel. A method for producing a high-strength, high-toughness cement-based material. 3. The method for producing a high-strength and high-toughness cementitious material according to claim 1, wherein the heating for recovering the shape memory of the fiber reinforcing material is performed by electromagnetic induction heating which hardly requires heating of the matrix. Method. The shape memory alloy used is Mn: 15 to 40% by weight, Si: 3 to 15% by weight, Cr: 0 to 20% by weight, Ni: 0 to 20% by weight, Nb: 0.1 to 1.5% by weight. , C: 0.01 to 0.2% by weight, with the remaining Fe and inevitable impurities as Cu: 3% by weight or less, Mo: 2% by weight or less, Al: 10% by weight or less, Co: 30% by weight or less , N: 5000 ppm or less, the atomic ratio of Nb to C is in the range of 1.0 to 1.2, and after processing at room temperature or in the temperature range of 500 to 800 ° C., 5 to 40%, The NbC-added Fe-Mn-Si-based shape memory alloy obtained by precipitating NbC carbide by aging heat treatment in a temperature range of 400 ° C to 800 ° C for 1 minute to 2 hours. For producing a high-strength, high-toughness cementitious material.

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