Fiber Reinforced Mortar

Abstract

To provide a fiber-reinforced mortar that has good workability and excellent initial and long-term strength development.SOLUTION: The fiber-reinforced mortar contains a fiber-reinforced mortar composition including quick-hardening cement, silica fume, fine aggregate and fibers, and water. A content of the silica fume is 10 to 35 pts.mass per 100 pts.mass of the quick-hardening cement, a content of the fine aggregate is 80 to 430 pts.mass per 100 pts.mass of the quick-hardening cement, a content of the fibers is 0.02 to 8 pts.volume per 100 pts.volume of the quick-hardening cement, and a content of the water is 25 to 50 pts.mass per 100 pts.mass of the quick-hardening cement.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a fiber-reinforced mortar composition and a fiber-reinforced mortar.

Background Art

[0002] In recent years, demands for taller, larger, and more durable building structures and civil engineering structures have become even clearer. In order to realize such buildings, the development of high-strength mortar has been carried out. As such high-strength mortar, for example, Patent Document 1 discloses an ultra-high-strength mortar containing at least cement, pozzolanic fine powder, fine aggregate having a particle size of 3.5 mm or less, a water reducing agent, and water.

[0003] Concrete used in various structures is inherently excellent in durability, but in some cases, a part of it may deteriorate depending on the structure and usage environment. Such deterioration causes a decrease in the strength of concrete, etc. Therefore, when repairing or reinforcing, short fibers are blended into the mortar composition for the purpose of following the deformation of the base structure and reducing cracks, and a fiber-reinforced mortar composition with improved properties such as tensile strength and toughness may be used (for example, Patent Document 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, in the case where the construction time is limited, such as in partial repair work of structures such as roads and railways, fiber-reinforced mortar is required to be easy to construct and quickly develop strength after construction. However, in conventional fiber-reinforced mortar compositions, there has been a problem that it is difficult to achieve both workability and initial and long-term strength development.

[0006] Therefore, an object of the present invention is to provide a fiber-reinforced mortar composition and a fiber-reinforced mortar that have good workability and are excellent in initial and long-term strength development.

Means for Solving the Problems

[0007] As a result of intensive studies on the above problems, the present inventor has found that by adjusting the contents of pozzolanic substances and fine aggregates and blending fibers in a specific volume ratio, it is possible to achieve both workability and initial and long-term strength development.

[0008] That is, the present invention is shown in the following [1] to [5]. [1] A fiber-reinforced mortar composition containing cement, a pozzolanic substance, fine aggregates, and fibers, wherein the content of the pozzolanic substance is 1 to 35 parts by mass with respect to 100 parts by mass of cement, the content of the fine aggregates is 80 to 430 parts by mass with respect to 100 parts by mass of cement, and the content of the fibers is 0.02 to 8 parts by volume with respect to 100 parts by volume of cement. [2] The fiber-reinforced mortar composition according to [1], wherein the pozzolanic substance contains silica fume. [3] The fiber-reinforced mortar composition according to [1] or [2], wherein the fibers are organic fibers. [4] The fiber-reinforced mortar composition according to any one of [1] to [3], wherein the length of the fibers is 1 to 30 mm. [5] A fiber-reinforced mortar containing the fiber-reinforced mortar composition according to any one of [1] to [4] and water, wherein the content of water is 25 to 50 parts by mass with respect to 100 parts by mass of cement.

Effects of the Invention

[0009] According to the present invention, it is possible to provide a fiber-reinforced mortar composition and a fiber-reinforced mortar that have good workability and excellent initial and long-term strength development properties.

Embodiment for Carrying Out the Invention

[0010] Hereinafter, an embodiment of the present invention will be described in detail.

[0011] The fiber-reinforced mortar composition of this embodiment contains cement, a pozzolanic substance, fine aggregate, and fibers.

[0012] Various cements can be used, for example, various Portland cements such as ordinary, early-strength, super-early-strength, low-heat, and medium-heat Portland cements, eco-cement, rapid-hardening cement, etc. The cement may be used alone or in combination of two or more.

[0013] From the viewpoint of better strength development at an early stage, rapid-hardening cement is preferable for the cement. The rapid-hardening cement preferably contains calcium aluminates as an active ingredient, and more preferably contains 11CaO·7Al2O3·CaX2 (X represents a halogen atom) or 3CaO·3Al2O3·CaSO4 (aluminate) as an active ingredient. 11CaO·7Al2O3·CaX2 is a so-called calcium aluminate halide-based cement. The halogen atom is preferably a fluorine atom. Also, aluminate is also referred to as calcium sulfoaluminate-based cement (aluminate-based cement). These are called ultra-rapid-hardening cements and are commercially available under the trade names Jet Cement or Super Jet Cement. The rapid-hardening cement is most preferably aluminate-based cement.

[0014] In addition, as calcium aluminates, when CaO is represented by C, Al2O3 by A, and Fe2O3 by F, calcium aluminates having mineral compositions represented by C3A, C2A, C12A7, C5A3, CA, C3A5, CA2, etc., calcium aluminoferrites represented by C2AF, C4AF, etc., alumina cement, and those in which SiO2, K2O, Fe2O3, TiO2, etc. are dissolved or combined therein are included. The calcium aluminates may be either crystalline or amorphous, or may be a mixture of crystalline and amorphous. A quick-setting admixture prepared by blending these calcium aluminates with inorganic salts such as gypsum can also be used as a quick-setting cement when added to Portland cement.

[0015] Pozolanic substances include various fly ashes described in JIS A 6201:2015, silica fume described in JIS A 6207:2016, slag powder, amorphous aluminosilicate, and the like. From the viewpoint of being more excellent in long-term strength development and workability, silica fume and amorphous aluminosilicate are preferable as the pozzolanic substances. The pozzolanic substances may be used alone or in combination of two or more.

[0016] The content of the pozzolanic substance is 1 to 35 parts by mass with respect to 100 parts by mass of the cement. When the content of the pozzolanic substance is outside the above range, the properties of the fiber-reinforced mortar are not excellent, the workability is deteriorated, or long-term strength development is difficult to obtain. From the viewpoint that the initial strength development and the long-term strength development are more likely to be compatible, the content of the pozzolanic substance is preferably 5 to 30 parts by mass, and more preferably 10 to 25 parts by mass with respect to 100 parts by mass of the cement.

[0017] The fine aggregate is not particularly limited, and examples thereof include river sand, silica sand, crushed sand, gypsum, limestone sand, slag aggregate, etc. Among these, silica sand is preferable as the fine aggregate. The fine aggregate may be used alone or in combination of two or more kinds. It is preferable to use the fine aggregate having a particle size of 5 mm or less (the portion passing through a 5 mm sieve), which is commonly used.

[0018] The content of the fine aggregate is 80 to 430 parts by mass with respect to 100 parts by mass of cement. If the content of the fine aggregate is outside the above range, the properties of the fiber-reinforced mortar are not excellent, the workability is reduced, and it is difficult to obtain strength development. From the viewpoint of further improving the workability, the content of the fine aggregate is preferably 100 to 350 parts by mass, more preferably 150 to 300 parts by mass, with respect to 100 parts by mass of cement.

[0019] Examples of the fibers include organic fibers such as vinylon fiber, polypropylene fiber, nylon fiber, and acrylic fiber; steel fiber; and inorganic fibers such as glass fiber. From the viewpoint of better dispersibility, the fibers are preferably organic fibers, more preferably vinylon fiber and polypropylene fiber. The fibers may be used alone or in combination of two or more kinds.

[0020] The length of the fibers is preferably 1 to 30 mm, more preferably 1.5 to 25 mm, still more preferably 1.8 to 20 mm, and most preferably 2 to 15 mm. If the length of the fibers is within the above range, the dispersibility in the fiber-reinforced mortar is further improved.

[0021] The content of the fibers is 0.02 to 8 parts by volume with respect to 100 parts by volume of cement. If the content of the fibers is outside the above range based on volume, the properties (fresh properties) of the fiber-reinforced mortar deteriorate and the workability is reduced. From the viewpoint of further excellent workability, the content of the fibers is preferably 0.05 to 7.5 parts by volume, more preferably 0.08 to 7 parts by volume, with respect to 100 parts by volume of cement.

[0022] As described above, the content of the fibers may be within the above range on a volume basis, but the content of the fibers on a mass basis is preferably 0.01 to 5 parts by mass, more preferably 0.03 to 3 parts by mass, and even more preferably 0.05 to 2.5 parts by mass with respect to 100 parts by mass of cement. If the content of the fibers is within the above range on a mass basis, the workability tends to improve.

[0023] The fiber-reinforced mortar composition of the present embodiment may contain an expansion agent. Any expansion agent may be used as long as it is a JIS-compliant expansion agent (JIS A 6202:2008) generally used as an expansion agent for concrete. Examples of the expansion agent include an expansion agent mainly composed of free quicklime (quicklime-based expansion agent), an expansion agent mainly composed of ettringite (ettringite-based expansion agent), and a composite expansion agent of free quicklime and ettringite product substance. Among these, the quicklime-based expansion agent is preferred. The expansion agent may be used alone or in combination of two or more. It is preferable to use an expansion agent having a Blaine specific surface area of 2000 to 6000 cm 2 / g.

[0024] The content of the expansion agent is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 8 parts by mass, and even more preferably 1 to 5 parts by mass with respect to 100 parts by mass of cement. If the content of the expansion agent is within the above range, the compressive strength, dimensional change rate, etc. will be even more excellent.

[0025] The fiber-reinforced mortar composition of the present embodiment may contain a water reducing agent. The water reducing agent includes a high-performance water reducing agent, a high-performance AE water reducing agent, an AE water reducing agent, and a fluidizing agent. Examples of such water reducing agents include water reducing agents specified in JIS A 6204:2011 "Chemical admixtures for concrete". Examples of the water reducing agent include polycarboxylic acid-based water reducing agents, naphthalene sulfonic acid-based water reducing agents, lignin sulfonic acid-based water reducing agents, melamine-based water reducing agents, and acrylic-based water reducing agents. Among these, the naphthalene sulfonic acid-based water reducing agent is preferred. The water reducing agent may be used alone or in combination of two or more.

[0026] The content of the water reducing agent is preferably 0.1 to 10 parts by mass, more preferably 0.3 to 5 parts by mass, and still more preferably 0.5 to 2.5 parts by mass with respect to 100 parts by mass of cement. If the content of the water reducing agent is within the above range, better fluidity and trowelability can be easily obtained when made into mortar, and the strength development during hardening is also more likely to be improved.

[0027] The fiber reinforced mortar composition of this embodiment may contain a setting retarder. Examples of the setting retarder include organic acids such as citric acid, gluconic acid, malic acid, tartaric acid, or salts thereof; borates such as boric acid and sodium borate, inorganic salts such as phosphates, alkali metal carbonates, and alkali metal bicarbonates; and saccharides. Among these, citric acid, citrate, tartaric acid, tartrate, and alkali metal carbonate are preferred. The setting retarder may be in powder form or in liquid form (for example, in the form of an aqueous solution, emulsion, or suspension). The setting retarder may be used alone or in combination of two or more.

[0028] The content of the setting retarder is preferably 0.1 to 8 parts by mass, more preferably 0.5 to 5 parts by mass, and still more preferably 0.8 to 3 parts by mass with respect to 100 parts by mass of cement. If the content of the setting retarder is within the above range, it is easier to ensure the workable time, and the initial strength development is less likely to decrease.

[0029] In the fiber reinforced mortar composition of this embodiment, various admixtures (materials) may be blended within the range that does not impair the effects of the present invention. Examples of the admixtures (materials) include gypsum, cement polymers, foaming agents, defoaming agents, waterproof agents, rust preventives, shrinkage reducing agents, water retaining agents, pigments, water repellents, efflorescence preventives, thickeners, dust reducing agents, strength enhancers, stone powder, and earth mineral powders.

[0030] The method for manufacturing the fiber-reinforced mortar composition of the present embodiment is not particularly limited. For example, it can be manufactured by mixing with a gravity mixer such as a V-type mixer or a tilting concrete mixer, or a mixer such as a Henschel mixer, an injection mixer, a ribbon mixer, or a paddle mixer.

[0031] The fiber-reinforced mortar composition of the present embodiment can be mixed with water to form a fiber-reinforced mortar, and the water content can be appropriately adjusted according to the application. In the fiber-reinforced mortar, the water content is preferably 25 to 50 parts by mass, more preferably 30 to 45 parts by mass, and still more preferably 33 to 42 parts by mass with respect to 100 parts by mass of cement. If the water content is within the above range, it is easier to ensure workability, and it is easier to suppress the occurrence of material separation, the increase in shrinkage of the hardened body, and the decrease in initial strength development.

[0032] The preparation of the fiber-reinforced mortar of the present embodiment can use the same kneading equipment as that of a normal fiber-reinforced mortar composition, and is not particularly limited. Examples of the kneading equipment include a mortar mixer, a grout mixer, a hand mixer, a tilting drum mixer, a twin-shaft mixer, and the like.

[0033] The fiber-reinforced mortar composition of the present embodiment has excellent workability because of its good fresh properties when it is made into mortar, and it is excellent in the initial and long-term strength development during hardening. Therefore, the fiber-reinforced mortar composition and the fiber-reinforced mortar of the present embodiment can also be suitably used in the repair of concrete structures such as roads and railways where rapid construction is required. Also, the construction method is not particularly limited, and methods such as filling the concave part with a trowel, leveling with a vibrator or the like after filling and then finishing with a trowel, and spraying on the repair part can be selected.

Examples

[0034] Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited thereto. All experiments were carried out at 20°C. The fiber-reinforced mortars of No. 7 and No. 9 are used as reference examples.

[0035] The materials used in the examples are as follows. Cement: Quick-setting cement (specific gravity 3 g / cm 3 , abbreviation C) Fine aggregate: Silica sand (particle size adjusted, abbreviation S) Pozolanic material: Silica fume (BET specific surface area 10.2 m 2 / g, abbreviation SF) Fibers: Nylon-based organic fiber (fiber length 5 mm, specific gravity 1.14 g / cm 3 , abbreviation F1) Fibers: Polypropylene-based organic fiber (fiber length 12 mm, specific gravity 0.91 g / cm 3 , abbreviation F2) Fibers: Nylon-based organic fiber (fiber length 20 mm, specific gravity 1.14 g / cm 3 , abbreviation F3) Fibers: Glass fiber (fiber length 24 mm, specific gravity 2.55 g / cm 3 , abbreviation F4) Expansion agent: Quicklime-based expansion agent Water reducer: Naphthalene sulfonic acid-based water reducer Setting retarder: Citrate

[0036] [Mix design of fiber-reinforced mortar composition] Based on 100 parts by mass of cement, fine aggregate, pozzolanic material and fibers were used in the ratios shown in Table 1, 2 parts by mass of expansion agent, 1.5 parts by mass of water reducer and 1 part by mass of setting retarder were used for mix design.

[0037] [Preparation of fiber-reinforced mortar] In an environment of 20 °C, 37 parts by mass of tap water was added to 100 parts by mass of cement in a 10 L cylindrical container, and each material of the fiber-reinforced mortar composition designed in Table 1 was added, and kneaded with a hand mixer for 60 seconds to produce about 3 L of mortar.

[0038] [Evaluation method] For each item, the evaluation was carried out by the following method. The evaluation results are shown in Table 1. 1) Compressive strength In accordance with the Japan Society of Civil Engineers Standard JSCE-G 5050-2010 "Test Method for Compressive Strength of Mortar or Cement Paste Using Cylindrical Specimens (Draft)", the compressive strengths at 3 hours and 28 days of age were measured. The dimensions of the specimens were 50 mm in diameter and 100 mm in height. The specimens at 28 days of age were demolded the next day and then cured in water until the age of curing. The curing was always carried out in a constant temperature bath at 20°C. 2) Fresh properties a) Dispersibility When producing fiber-reinforced mortar with a hand mixer, if the fibers were not uniformly dispersed due to the occurrence of fiber clumps or the like, it was evaluated as defective (×), and if it was confirmed that the fibers were uniformly dispersed, it was evaluated as good (○). b) Softness In accordance with JIS R 5201:2015 "Physical Test Methods for Cement", item 12. Flow Test, it was measured under an environment of 20°C. Standard samples without fibers were prepared for each formulation of fiber-reinforced mortar, and the 15-beat flow of these was measured. Next, the 15-beat flow of each fiber-reinforced mortar was measured. If the value of the 15-beat flow of each fiber-reinforced mortar was less than 80% compared to the flow value of the corresponding standard sample, it was evaluated as defective (×), and if it was 80% or more, it was evaluated as good (○). c) Finishability Fiber-reinforced mortar was placed in a mold (30 cm × 30 cm × 2 cm), and the finishability was evaluated by troweling. If it took a little time for the finishing work (more than 5 minutes from the time of placement until the completion of the finishing work), it was evaluated as ○, and if it was not aesthetically good (such as the mortar surface being slightly uneven), it was evaluated as ×. Otherwise, it was evaluated as ◎.

[0039]

Table 1

[0040] The fiber-reinforced mortar of the example had good fresh properties, so the workability was good, and the strength development at 3 hours and 28 days of age was also high. On the other hand, the fiber-reinforced mortar of the comparative example had inferior fresh properties or inferior strength development.

Claims

1. A fiber-reinforced mortar composition comprising a rapid-hardening cement, silica fume, fine aggregate, and fibers, and water, wherein the rapid-hardening cement is an aluminate-based cement, the fibers are organic fibers or inorganic fibers, the content of the silica fume is 10 to 35 parts by mass with respect to 100 parts by mass of the rapid-hardening cement, the content of the fine aggregate is 80 to 430 parts by mass with respect to 100 parts by mass of the rapid-hardening cement, the content of the fibers is 0.02 to 8 parts by volume with respect to 100 parts by volume of the rapid-hardening cement, and the content of the water is 33 to 50 parts by mass with respect to 100 parts by mass of the rapid-hardening cement, a fiber-reinforced mortar.

2. Measured in accordance with the Japan Society of Civil Engineers Standard JSCE - G 5050 - 2010 "Test Method for Compressive Strength of Mortar or Cement Paste Using Cylindrical Specimens (Draft)", the compressive strength at 28 days of age is 78 N / mm ２ or more, the fiber-reinforced mortar according to claim 1.

3. The compressive strength at 3 hours of age, measured in accordance with the Japan Society of Civil Engineers Standard JSCE - G 5050 - 2010 "Test Method for Compressive Strength of Mortar or Cement Paste Using Cylindrical Specimens (Draft)", is 39 N / mm ２ The fiber-reinforced mortar according to claim 1 or 2, wherein the above is satisfied.

4. The fiber-reinforced mortar according to Claim 1, further comprising an expansion agent.

5. The fiber-reinforced mortar according to Claim 1, further comprising 1.5 to 10 parts by mass of a water reducing agent with respect to 100 parts by mass of the rapid-hardening cement.

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