JPH0119323B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is a novel manufacturing method for PS concrete products, and more specifically, by embedding a metal wire in a molded body and applying tension to it, compressive stress is generated as a reaction force to the tension, thereby increasing mechanical strength. The present invention relates to a method for producing increased PS concrete products. Concrete products in which metal wires such as steel wires are embedded to increase the strength in the longitudinal direction are called P.S. concrete products, such as bridge girders,
Widely used for dam building materials, sleepers, etc. This PS concrete product is usually manufactured by stretching metal wires such as steel wires in a frame, and pouring cement mortar into it and hardening it. It is known that when the tension is released, compressive stress is generated due to the contraction of the elongated metal wire, and the strength is increased. It is also known that when producing concrete products, an expanding admixture is generally added to cement mortar to expand its volume, and that the products thus obtained have a lower cracking rate. However, in the conventional manufacturing method of PS concrete products, special equipment is required to stretch the metal wire within the frame in advance, and extra operations for tensioning and releasing are required, which makes production difficult. There is no escape from a decline in sexuality. In order to solve these problems with the conventional method, the present inventors have developed a method of applying tension to the metal wire that can generate sufficient compressive stress in the cement mortar without actively applying tension to the metal wire. In order to develop a method for applying tension, various studies were conducted, and an attempt was made to add tension to the metal wire by mixing an expanding admixture into cement mortar and utilizing the expansion action of the concrete during molding, but this method was not successful. The adhesion between the mortar and the metal wire was insufficient, making it impossible to generate tension in the metal wire, making it impossible to achieve the objective. As a result of further research, we found that by using a short fiber material together with an expandable admixture, the adhesion between the metal wire and mortar was surprisingly improved, and sufficient tension could be imparted to the metal wire. The present invention was developed based on this finding. That is, according to the invention, 100 parts by weight of cement, 1 to 20 parts by weight of short fiber material, and 5 parts by weight of expandable admixture.
Cement mortar containing ~22 parts by weight as an essential component is formed into a predetermined shape using a metal wire as a core material, and then cured to allow the cement components to harden and expand while applying tension to the core material.
Compressive stress is generated in the cement mortar as a reaction force, and PS concrete products with excellent mechanical strength can be manufactured. In the present invention, since the short fibers are present in the cement mortar together with the metal wire, they become tensed during the cement mortar hardening and expansion process, and compressive stress due to the contraction force acts on the steel wire. Therefore, it is considered that sufficient adhesive force is generated between the cement mortar and the steel wire. In addition, it has been discovered that if cracks occur in PS concrete products for some reason, they tend to propagate along wire rods such as steel wires, and that the addition of cement expansion agents can prevent cracks to some extent. However, in the present invention, short fibers are blended in addition to the expanding agent for cement, so the compressive stress of the short fibers scattered inside the concrete product can spread along steel wires, etc. The cracks that occur are interrupted, and together with the above-mentioned adhesive strength, the crack resistance is significantly improved. The cement used in the method of the present invention can be arbitrarily selected from hydraulic substances generally referred to as cement in a broad sense. Examples of such cements include Portland cement, early strength cement, alumina cement, blast furnace cement, silica cement, and fly ash cement, but ordinary Portland cement is preferred. In the present invention, the term "expandable admixture" refers to a material that has the property of forming a hardened structure different from that of cement and expanding after cement mortar has hardened to a certain extent.・Denka containing aluminate components
Examples include CSA (trade name, Denki Kagaku Kogyo Co., Ltd.), Asano Dipcal (trade name, Nippon Cement Co., Ltd.), and Expan (trade name, Onoda Cement Co., Ltd.) containing a calcium oxide component. The amount of the admixture used is in the range of 5 to 22 parts by weight based on 100 parts of dry weight of cement, preferably 7 parts by weight or more, more preferably 10 parts by weight or more. If the content is less than 5 parts by weight, the effect will not be sufficient, and if it exceeds 22 parts by weight, the mortar will expand significantly and the strength of the mortar itself will decrease, furthermore, there is a tendency for cracks to occur. Although the short fiber material is not particularly used for reinforcement in the present invention, short fibers used in conventional resin/short fiber composites can be advantageously employed in the present invention. Such materials include inorganic fibers such as asbestos, rock wool, mineral wool, ceramic wool, silica fibers, metal fibers, carbon fibers, and glass fibers, as well as organic synthetic fibers and natural fibers. The length of these fibers is 2 to 60 mm, preferably 3
It is about ~50mm. The amount used is cement 100
It ranges from 1 to 20 parts by weight, and usually about 2 to 15 parts by weight. In addition, in the present invention, it is desirable that the adhesion affinity with hardened cement is higher than that of steel fibers, and from that point of view, asbestos, rock wool, mineral wool, ceramic wool,
Silica fiber, steel wool, etc. are preferred. As the metal wire, those used in conventional PS concrete can be used, and typically there are metal wires such as steel wire and iron wire. Note that it is also possible to use a continuous material such as those exemplified as the short fiber material, which has a strength equivalent to that of a metal wire. The metal wire rod is embedded in concrete as a core material of PS concrete, and exhibits its effect according to the present invention. PS concrete products are characterized by strength in the direction of the core material, so in the case of bar-shaped products, the strength is in the longitudinal direction, and in the case of substantially plate-shaped products, the strength is in the longitudinal direction or in the length and lateral direction. The core material is appropriately arranged in two directions. The above-mentioned molding means shaping the cement mortar into a desired shape using the metal wire as a core material, and for example, known molding methods such as pour molding, press molding, spray molding, extrusion molding, and injection molding can be adopted. . In the case of extrusion molding, it is effective to embed the core material using, for example, an extrusion die similar to that used in known electric wire coating methods. The above-mentioned cement mortar generally contains the above-mentioned essential components and an appropriate amount of water, and further optionally contains additives such as water-reducing agents and plasticizers, and at least one component of known aggregates. The curing mentioned above refers to a process of hardening and expanding cement mortar components. That is, in the present invention, this refers to the step of expanding the cement mortar after the cement component hardens and substantially adheres to the core material and short fibers. This can be achieved to some extent by leaving it after molding, but as a preferred process, for example (a) leaving it for several hours (e.g. 4 to 6 hours or more) after molding, and then heating it in a steam atmosphere at 40 to 60°C for 3 to 30 minutes. (b) Leave for 12 to 24 hours after molding, then cure in water for 2 days or more; (c) Leave for 4 to 6 hours or more after molding, then heat at a relative humidity of 70% or more. Examples include curing in a humid air for more than a day. In addition, in the case of extrusion molding (or injection molding),
If the amount of staple fiber material exceeds 20 parts by weight, extrusion can be problematic, so it is generally advantageous to use less than in the case of casting. In the former case, the short fibers tend to be aligned in the extrusion direction, so the effect is fully exhibited. In the case of extrusion molding, the fiber length is 2 to 40 mm.
The thickness is desirable, and more preferably about 3 to 30 mm. Further, as the fiber, highly flexible fibers such as asbestos and rock wool are preferred. The product according to the invention can be effectively applied to the field of conventional PS concrete and especially to the field of structural materials requiring mass production. Further, because of the simplicity of the manufacturing method, it can be advantageously applied to structural base materials, such as substrates for tile panels as described below.
That is, an embodiment is exemplified in which the above-mentioned molded product is molded into a substantially flat plate shape on the back surface of a decorative material such as a tile, and both are bonded and cured simultaneously. The present invention will be explained in more detail below using specific examples of pour molding and extrusion molding, but the present invention is not limited to these examples, and modifications and variations of the examples are naturally possible. Note that the measured value in each example is the average value of three samples. Example 1 100 parts by weight of ordinary Portland cement, 0 to 25 parts by weight of expansive admixture (Denka CSA #20), 5 parts by weight of asbestos, 100 parts by weight of Toyoura standard sand, 33 parts by weight of water, 1 part by weight of water reducing agent (Mighty 150) After kneading the weight part, it was poured into a 4 x 4 x 16 cm mold and molded. At that time, seven hard steel wires of 1 mm diameter were placed at equal intervals in the length direction of a 4 x 16 cm plane at positions 5 mm from the end surface. Buried. The molded product was left for 1 day, then demolded, cured in water at 20°C for 6 days, and then heated at 20°C x 60% for 21 days.
RH air curing was performed. The product was placed so that the hard steel wire reinforcement part was on the lower side, and a load was applied at a rate of 1 mm/min using an autograph (manufactured by Shimadzu Corporation), and the crack resistance strength at that time was measured. The results are shown in Table 1. In addition, the numerical values other than the strength in the table indicate the blending amount (parts by weight).

[Table] Comparative Example The process and measurements of Example 1 were carried out with the amount of the expansive admixture being 17.6 parts by weight and without using either or both of the asbestos staple fibers and the hard steel wire. The results are shown in Table 2.

【expressed.
As is clear from Table 2, when reinforced with asbestos short fibers or steel wire and given a chemical prestress effect, the
There was an increase in strength of 70kgf/cm ² . However, as shown in the example in Table 1, when 17.6 parts by weight of Denka CSA #20 is added and reinforced with both short asbestos fibers and steel wire reinforcement, the crack resistance is 233 kgf/
cm ² , and when compared with the theoretical value of 138 kgf/cm ² , the strength increased by 95 kgf/cm ² . This indicates that the combined use of both asbestos short fibers and steel wire reinforcement had a greater effect than when they were used alone. Example 2 100 parts by weight of ordinary Portland cement, Denka
17.6 parts by weight of CSA #20, 100 parts by weight of standard sand from Toyoura,
Plasticizer (Himetrose manufactured by Shin-Etsu Chemical Co., Ltd.)
90SH4000) 2.4 parts by weight, asbestos (Australian)
After kneading 5 parts by weight of S6D-20) and 35 parts by weight of water, use an extruder (manufactured by Miyazaki Iron Works Co., Ltd.) to create a 50×10×160
Five hard steel wires of 1 mmφ were embedded at equal intervals and extruded to the size of . After leaving the molded product moist for 1 day, curing in water at 20℃ for 6 days, and 21 days at 20℃×60%
RH air curing was performed. The crack resistance strength of the product was measured by applying a load at a speed of 1 mm/min using an Autograph (manufactured by Shimadzu Corporation) and found to be 265 kgf/cm ² . Example 3 A tile panel was manufactured using the asbestos-containing cement mortar in Example 1, in which the amount of expansive admixture was 17.6 parts by weight. A large number of approximately 10 cm square ceramic tiles were placed in the formwork with their backs facing upwards, the mortar was poured in, a 1 mmφ hard steel wire was installed, and the mortar was poured in again, followed by curing in the same manner as in Example 1. It was carried out in The dimensions of the tile panel were 90 x 180 cm and the weight was 58.5 kg. The thickness of the hardened mortar part was 25 mm. The hard steel wires were buried 5 mm from the bottom at intervals of approximately 10 cm in both the longitudinal and lateral directions. The product thus obtained was found to be lighter in weight than conventional products, but to have sufficient strength as a self-supporting wall material.

Claims (1)

[Scope of Claims] 1. A cement mortar containing as essential components 100 parts by weight of cement, 1 to 20 parts by weight of a short fiber material, and 5 to 22 parts by weight of an expansive admixture is formed into a predetermined shape using a metal wire as a core material. A method for producing a PS concrete product, which is then cured to cause the cement components to harden and expand, and to apply tension to the core material to generate compressive stress in the compact. 2. The manufacturing method according to claim 1, wherein the molding is performed by pour molding or press molding. 3. The manufacturing method according to claim 1, wherein the molding is performed by extrusion molding.