JPS63552A - Fiber reinforced cementicious member - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a fiber-reinforced cement-based member in which air-fiber reinforcing materials are arranged and embedded in a cement-based matrix.

<Prior Art> Generally, fiber-reinforced cement-based members are widely used as members for civil engineering and construction in the form of plates, cylinders, hollow plates, blocks, and the like.

Traditionally, so-called asbestos slate was a typical example of fiber-reinforced cement-based members, but recently, from the perspective of preventing environmental pollution caused by asbestos, various organic, inorganic, and metal (rho fibers) are being used as reinforcement material. It has become.

<Problems to be Solved by the Invention> However, most of these materials are manufactured by a method of dispersing 9-dimensionally or 3-dimensionally randomly into a cement matrix, so that high-strength and high-toughness molded products cannot be obtained. It takes a large amount of fiber to obtain this, and there is a lot of waste.

Particularly when using high-performance fibers, there is a drawback that the strength and elasticity of the fibers cannot be fully exploited, leading to high costs and problems.

For this reason, a method has been considered in which the long fibers are formed in advance into a linear or lattice shape, and the fibers are oriented one-dimensionally or two-dimensionally in the cross section of the cement matrix to improve the physical properties of the molded product.

According to this method, a smaller amount of fibers is required to obtain the same bending or tensile strength than a molded article with two-dimensional or three-dimensional random orientation, and it is possible to design the material, and the higher the performance of the fiber, the higher its mechanical performance. It has the advantage that it can be used effectively.

- On the other hand, high-quality wires and fibers such as carbon fiber, aramid fiber, alkali-resistant glass fiber, and high-strength vinylon fiber have significantly higher tensile strength than cement-based materials themselves, so cement-based components equipped with these fibers This has the effect of increasing the maximum tensile or bending stress.

However, in addition to having high tensile strength, these high-performance fibers have a high tensile modulus with a tensile elongation at break of only a few inches or less.

Among these, carbon fiber has the advantage of being highly durable without the problem of deterioration caused by the alkalinity of cement, and can withstand high-temperature steam curing during the manufacture of the component. Carbon fiber has an extremely high tensile modulus of elasticity with a tensile elongation at break of about 1 inch or less. It is a fiber.

Therefore, in *, m-reinforced cement-based members using these high-performance fibers with small tensile elongation at break, the fibers will break when the maximum tensile or bending stress is reached, resulting in small tensile strain or bending deflection. It has the disadvantage of poor deformability and toughness.

Therefore, conventional techniques to improve such stress and toughness are as follows: ■ The amount of fiber in the lower half of the plate thickness is larger than that in the upper half, and the amount of aggregate i in the lower half of the plate thickness is smaller than that in the upper half. Toshi Kui fiber reinforced cement board (Japanese Unexamined Patent Publication No. 5≠-/504t, No. 20), ■ A lower layer of reinforcing sandalwood with a large amount of fibers mixed in, and an upper layer with a small amount of fibers mixed as needed. The thickness of the lower layer is 0.0% relative to the total thickness of the upper and lower layers. Fiber-reinforced cement board that is said to be ≠~0.7 times
(Hiroshi Publication), ■ Jf+I from the surface! l# fiber-reinforced cement hardened material in which the fibers are dispersed and oriented in the surface layer within n (Japanese Unexamined Patent Publication No. 7-//r&/), or ■ Stir layered mesh using steel mesh as a stress material. High-toughness ferrocement board formed by interposition (Japanese Patent Application Laid-Open No. 1983-1999-/,
2!606), etc. are known.

However, due to their power, these conventional techniques still have the following problems.

That is, in the cases of ■ to ■, although providing a fiber reinforcing layer in the area of the bending member where tensile stress acts has the effect of increasing the bending stress, the maximum bending stress is reached;
When the fibers break, the stress level decreases rapidly, and it is difficult to create a member with excellent toughness that can maintain a sufficiently large stress level in the range of bending deflection that exceeds the maximum bending stress level.

In the case of (2), the steel mesh used for reinforcing corrodes under severe usage conditions or over a long period of time, resulting in poor durability.

<Means for Solving the Problems> Therefore, the inventors of the present invention have conducted extensive studies in view of the above problems, and have found that when arranging at least two layers of long fibers in the area where tensile stress acts on a cement-based bending member, We have discovered that these problems can be solved by using long fibers with different tensile strengths and by arranging long fibers with a high tensile strength at a position close to the neutral bending axis of the member, and have arrived at the present invention. .

That is, an object of the present invention is to provide a fiber-reinforced cement-based member with high strength and toughness by arranging reinforcing fibers in a small amount and with an excellent reinforcing effect.

The purpose is to create a fiber-reinforced cement-based member that is subjected to bending stress, and the tensile stress of the member is such that long fibers with different tensile strengths are placed in the area where the tensile stress acts with respect to the neutral axis of the bending stress of the member. At least two or more layers are arranged so as to bear the burden, and long fibers with greater tensile strength are used,
This can be easily achieved by arranging the fibers closer to the neutral axis.

The present invention will be explained in detail below.

The cement used in the present invention is not particularly limited as long as it is a hydraulic cement that is normally used for manufacturing cement products, as well as ordinary Portland cement, early strength Portland cement, blast furnace cement, and alumina cement.

The long fibers used may be of any material, such as organic or inorganic, but high-performance fibers such as carbon fibers, aramid fibers, alkali-resistant glass fibers, and high-strength vinylon fibers are particularly preferred.

An example of a method for disposing long fibers in a cement matrix according to the present invention is shown in FIG.

In FIG. 1, / is a fiber-reinforced cementitious member subjected to bending stress by a center-point loading bending test.

ko is the neutral axis of bending stress of the member (Nyl line in Figure 1)
, the area where tensile stress acts (N - N in Figure 1)
' line below) so that the tensile stress of the member can be made negative, and at a position closer to the neutral axis (the first
The long fibers are arranged at a distance from the neutral axis (represented by *T-1 in the figure) and have a large tensile strength.

Here, it is preferable that the longitudinal direction of the long fibers is the same as the direction of the tensile stress of the member, since the effect of bearing the tensile stress is most easily achieved. However, even if the longitudinal direction of the long fibers is not exactly the same as the direction of the tensile stress of the member, the directions may be slightly different as long as the tensile stress can be substantially borne.

3 has a smaller tensile strength and is arranged in the same longitudinal direction as Fico except that it is located further away from the neutral axis (represented by the distance L2 from the neutral axis in Fig. 1), and has an arranged length. It is a fiber.

Here, the tensile strength of the fibers as referred to in the present invention is expressed as a value between the tensile strength per unit cross-sectional area of the transverse cord used and the cross-sectional area of the fibers disposed in the cement matrix.

The tensile strength and cross-sectional area can be measured by the method of TI8 standard R760/, for example, in the case of low-feeding charcoal, and can be measured in accordance with the same method in the case of other fibers.

What is important in this invention is in the cement matrix! , where two or more layers of fibers are arranged, and the tensile strength of the long fibers F arranged near the neutral axis of the tensile stress of the member is higher than that of the multi-fibers arranged far from the neutral axis. It is also important to arrange the area so that it is easy for dogs to listen to it. FIG. 2 shows a load-deflection curve during bending of a fiber-reinforced cement-based member provided with long fibers as in the present invention.

In other words, as the deflection increases, the multi-fibers with low tensile strength, which are located far from the neutral axis and are subjected to large tensile strain, break first, and the load decreases slightly, but the fibers are located closer to the neutral axis. The load increases again due to the reinforcing capacity of the 4 m fibers, which are still unbroken and have a high tensile strength and are subjected to a small tensile strain. Eventually, the fibers themselves, which have a high tensile strength, break and the load gradually decreases to zero.

On the other hand, if long fibers with the same tensile strength are placed at positions far from the neutral axis and near the neutral axis, the load at the time when the long fiber at the far position breaks is as shown in Figure 2. Although υ is larger than in case a, the strength of the fibers at nearby positions is smaller than in case a, so the drop in load is large, and when further deflection is added, there is no large increase in load, and it is Fibers at nearby locations also break, and their deflection g is smaller than in the case of a.

In addition, contrary to the case of Snake, if the long fibers placed in the far position have a higher tensile strength, the fiber in the far position breaks as shown in Figure 1 C, and the load at the next point is the largest. However, since the strength of the fibers in the nearby positions is low, the drop in load is greatest, and when further deflection is applied, the fibers in the nearby positions break with almost no increase in load, and the amount of deflection becomes smaller than in case a.

In this way, from the comparison of the three different tensile strengths, K, which maintains a sufficiently large stress level and produces a bending member with excellent toughness when deflection is applied beyond the maximum bending stress level, is the original value. It is clear that it is preferable to arrange the fiber ## having a higher tensile strength as in the invention so as to be located close to the total neutral axis.

In the present invention, the method of arranging the long fibers with different tensile strength depending on the arrangement position is to use long fibers with the same type of tensile strength, and to arrange a large amount of the long fibers at a position closer to the neutral axis. By increasing the cross-sectional area and increasing the tensile strength obtained as the product of tensile strength and cross-sectional area, or by using two or more types of fibers with different tensile strengths, There is a method in which the tensile strength of each fiber is determined as the product of the tensile strength and the cross-sectional area of the fibers, and the fibers are arranged so that the fiber strength at a position close to the neutral axis is large. More specifically, the value of each fiber strength depends on factors such as the tensile strength and cross-sectional area of the fibers used, the distance of each fiber from the neutral axis, and the dimensions of the fiber-reinforced bending member. It can be set appropriately to obtain the bending stress and deflection required for the member, and the fiber strength at a position close to the neutral axis is equal to
# It is arranged so that it is 7 times or more stronger than the strength, preferably 7.5 to 4c times, more preferably 2 to 3.5 times.

Further, in order to obtain better bending toughness in the present invention, it is preferable to use a combination of two or more types of K having long fibers with different elongations at break.

For example, the elongation at break is different. When 2v4 class fibers are used and arranged as in the present invention, the load-deflection curve of the #2 fiber reinforcing member in bending will shift to a position farther from the neutral axis as the deflection increases, as shown in Figure 3a. The fiber with a small elongation at break breaks first, and the load decreases slightly, then the fiber with a small elongation at break near it breaks, and then the fiber with a large elongation at break, which is further away from the neutral axis, breaks! The bending mode is such that the male fiber breaks, and finally the fiber with a large breakage elongation near the end breaks.

In contrast, Figure 3 shows one type of #1 with the same elongation at break.
! This is the case where m is used and arranged as in the present invention. As can be seen from the comparison of the two, by using a combination of fibers with different elongations at break, the load drop during deflection is small, and while maintaining a large load, it is possible to increase deflection, resulting in an extremely superior member with high toughness. can get.

Judging from the bending mode when using two types of fibers with different elongations at break, if more types of fibers with different elongations at break are used in combination, it is possible to maintain a large load while achieving a larger bending mode. Flexibility can be achieved and a member with superior toughness can be obtained.

Furthermore, in the present invention, in order to obtain a large degree of bending stress,
It is preferable to use a combination of two or more types of fibers with different tensile moduli, and to arrange #32 fibers having a high tensile modulus at a position far from the neutral axis. For example, if fibers with a large tensile modulus are placed far from the neutral axis and fibers M with a small modulus are placed close to the neutral axis, the load-deflection curve will be as shown in Figure a. Compared to the curve of No. 1 Hirozu, in which only fibers are arranged in two layers, the load at the same deflection is much greater, and a member with high bending strength can be obtained, which is preferable.

In the present invention, the long fibers are arranged in at least two or more layers. Here, "arranging them in a substantially KJd shape" means that the long fibers are arranged in a substantially KJd shape when almost the same tensile stress is applied to the neutral axis of the tensile stress of the member. This means that the distances from the neutral axis are approximately the same in the regions to which they are applied. The number of long fibers arranged in a layered manner is not particularly limited, and is determined as appropriate depending on the strength effect desired to be imparted to the member.

Next, in the present invention, the long fibers used are usually a bundle of several hundred to several hundred single yarns having a diameter of several microns to several tens of microns.

In order to ensure the tensile strength of the bundle when placed in the cement matrix and to prevent damage during handling,
It is preferable to use the yarn by impregnating and adhering various polymeric substances to bind the single yarns together.

As specific polymeric substances, epoxy resin, urethane resin, phenol resin, polyvinyl alcohol, etc. are used.

In addition, in order to improve the adhesion with the cement matrix,
The fibers are subjected to surface treatment such as surface oxidation treatment, or an uncured epoxy resin with a softening point of 4 AO°C or higher is used as the polymer substance to be attached, or a carboxyl-modified rubber polymer is completely attached on top of the epoxy resin layer. Any method may be used.

In order to further improve the adhesion to the cement matrix, fine sand or the like may be further attached using a resin to the surface impregnated with the polymeric substance to provide an anchoring effect to the cement matrix.

In the explanation so far, the tensile strengths are different. The method of arranging two types of fibers by changing their positions with respect to the neutral axis has been described, but in the present invention, as long as the tensile strength is different from Co f-II class or more, a larger number of fibers can be used. There is no problem in using different types of fibers, and in that case, it is sufficient to arrange them so that they are located closer to the neutral axis than the amount of fibers with higher tensile strength.

Further, the shape of the long gauze W used in the present invention is not limited to a linear one-dimensional shape, but can also be formed into a lattice shape, a net shape, or a woven shape, and can be laminated two-dimensionally. Especially in the case of reticular
If the fibers are arranged in the longitudinal direction of the bond Q (I) referred to in the present invention, the strength will be higher.
This is preferable because a fiber reinforced member with high toughness can be obtained.

t6t= Embedding can be done using conventional methods.

For example, the conventional M layer/embedding layer may be used, or the matrix material may be injected and cured after being three-dimensionally assembled in a mold.

At this time, if the i2 is removed by applying vibration using a sintering device or the like, the adhesion between the cement matrix and the reinforcing +a 4M aggregate becomes even tighter, and good mechanical properties can be obtained.

Further, the member of the present invention may be a bent member such as a plate, a cylinder, a hollow plate, or a block, and its shape is not particularly limited.

<Effects of the Invention> As described above, according to the present invention, an extremely simple method of adjusting the tensile strength tX according to the placement position of the fibers is effective and rational with a small amount of fibers. It is possible to obtain a cement-based member that exhibits excellent reinforcing performance and has excellent bending toughness and strength.

Also, like reinforced concrete structures, cross-sectional designs can be effectively and easily tailored to the application, load, and conditions, making it highly practical.

EXAMPLES Hereinafter, the present invention will be explained in detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

Example / Mesophase high elongation carbon fiber made from coal tar pitch (consisting of about 4 cooo single filaments with a diameter of about 77 microns) was impregnated with an epoxy resin solution containing a curing agent diluted with acetone and cured by heating. and resin content IA7%
A linear long fiber was obtained, and its physical properties are shown in Table 1.

These 8NNl2 were bonded in the papier-mâché direction with epoxy adhesive and made into 7 bundles. 1), five bundles were arranged at equal intervals so that the longitudinal direction of the core fibers was the same as the tensile stress direction.

Table 1 shows the total cross-section and tensile strength of the five bundles.

On the other hand, five of the same long fibers were placed at a distance of 7°C from the neutral axis (represented by L2 in Figure 1) so that the longitudinal direction was the same as the tensile stress direction of the member. They were arranged at equal intervals, and their cross-sectional areas and tensile strengths are shown in Table 1.

The cement used was early-strength Portland cement, the aggregate used river sand (maximum 2.j tra + grain size), the water/cement ratio was θ, and the 4L/c aggregate/cement ratio was θ, 47//.

Span 7 of the fiber-reinforced cement-based specimen after curing for /week!
A center-point loading bending test was conducted at t Otvn, and the resulting bending stress-deflection curve is shown in Figure J. Furthermore, what is the bending strength of a single cement-based specimen without fiber reinforcement? /k
It was V/ad.

Comparative Example/The same long fibers as in Example/ were spliced into 7 bundles in the same way as in Example/, and 5 bundles each were placed at a distance of 2 and 5 from the neutral axis. was installed.

Their cross-sectional areas and tensile strengths are shown in Table 1, and the resulting bending stress-deflection curves are shown in Figure 5.

Comparative example / Same 9 long fibers as Example / were placed at a distance of Kosa from the neutral axis,
5 bundles made by joining 7 bundles of 3 same long fibers 7 m from the neutral axis
placed at a distance of

Their cross-sectional areas and tensile strengths are shown in Table 1, and the obtained bending stress-deflection curve M4 is shown in Figure J, C.

Example λ A mesophase low elongation carbon fiber made from coal tar pitch (consisting of about -2000 single filaments with a diameter of about 70 microns) was used in the same manner as in Example 1, and the resin content was increased.
Straight long fibers were obtained and their physical properties are shown in Table 1.

Two bundles of these #3 low elongation long fibers joined to form 7 bundles and 3 bundles of high elongation long fibers of Example/are 5ttr from the neutral axis.
They were arranged at equal intervals at a distance of tn.

-High elongation long line #≠ of Example/at a distance of 2 points from the neutral axis
A total of j books and the above-mentioned low elongation long fiber cloth/books were arranged at equal intervals.

Their cross-sectional areas and tensile strengths are shown in Table 1, and the resulting bending stress-deflection curves are shown in FIG.

Using "Alfiber J ARR21AO'0TF3", linear long fibers were obtained in the same manner as in Example, and the physical properties are shown in Table 1.

Is this glass length R1? Two fibers joined together to form seven bundles are called 3
The bundle and the high elongation carbon long wire #λ of Example were joined to form seven bundles, which were arranged at equal intervals at a distance from the neutral axis.

On the other hand, the same glass length # at a distance of 71 an from the neutral axis! One fiber and two high elongation carbon long fibers were arranged at equal intervals.

Their cross-sectional areas and tensile strengths are shown in Table 1, and the resulting bending stress-deflection curves are shown in FIG.

Example Hiromiara Lv fiber (manufactured by DuPont, USA, trademark "Kevlar≠")
2"/Hiroshi, 20 denier), linear long fibers were obtained in the same manner as in Example/, and the physical properties thereof are shown in Table 1.

A. One 7ξ length ma was spliced into seven bundles, and the long fibers λ used in Example 3 were arranged at equal intervals at three distances from the neutral axis.

On the other hand, similar aramid long fibers at a distance of two gates from the neutral axis≠
The books and seven long glass fibers were arranged at equal intervals.

Their cross-sectional areas and tensile strengths are shown in Table 1, and the resulting bending stress-deflection curves are shown in FIG.

[Brief explanation of the drawing]

Figure 1 is a plan view and cross section of liR, a reinforced cement-based member. Figures 2 to 2 are diagrams for explaining load-deflection curves in bending tests of fiber-reinforced cement-based members in the present invention. FIG. J-1 shows bending stress-deflection curves during bending tests of fiber-reinforced cement-based members in Examples and Comparative Examples of the present invention. / Fiber-reinforced cement-based member 2 Long edges with higher tensile strength, fibers 3 Long fibers with lower tensile strength Ll Distance from the neutral axis of long fibers with higher tensile strength L2 Long fibers with lower tensile strength Distance from neutral axis Applicant Mitsubishi Chemical Industries, Ltd. agent Patent attorney Necessity -N uniform ~ l/+
) Ko 1 Figure 2nd Heaven 3 Snake T-Shun and Figure 4 Tariyuki Kurezu Tomo B Rikihide (k5/cm)

Claims (4)

[Claims] (1) A fiber-reinforced cement-based member that is subjected to bending stress, in which long fibers with different tensile strength are used to bear the tensile stress of the member in the region where tensile stress acts with respect to the neutral axis of the bending stress of the member. At least substantially two or more layers are arranged so that
A fiber-reinforced cement-based member characterized in that long fibers with greater tensile strength are arranged at a position closer to the neutral axis among the long fiber arrangement positions. (2) The tensile strength of the long fibers arranged closer to the neutral axis of the member is 1.2 times or more the tensile strength of the long fibers arranged further away from the neutral axis. The member according to claim 1. (3) The member according to claim 1 or 2, wherein the long fibers have different elongations at break. (4) The member according to claim 1, wherein the long fibers are carbon fibers, aramid fibers, alkali-resistant glass fibers, or vinylon fibers.