JP6606782B1 - Method for producing super dense cement composition - Google Patents

Abstract

The present invention proposes a method for producing a super dense cement composition in which fibers can be uniformly dispersed and a denser super dense cement composition having low air permeability can be produced. A method for producing a super dense cement composition comprising a mixture of cement, silica fume, limestone filler, reinforcing fiber, water, a water reducing agent, and an antifoaming agent. A first mixing process in which half of the reinforcing fiber, cement, silica fume and limestone filler are kneaded to form a powder mixture, and water, a water reducing agent and an antifoaming agent are added to the powder mixture and mixed to make a cement system A second mixing step for generating a matrix and a third mixing step for adding and mixing the remaining amount of reinforcing fibers to the cement-based matrix are sequentially performed. [Selection] Figure 1

Description

  The present invention relates to a method for producing a super dense cement composition.

Concrete and mortar form a hardened body having the necessary strength and shape by solidifying the aggregate with a binder such as cement. Among these, concrete is formed by kneading a binder such as cement, water, coarse aggregate, fine aggregate, admixture and the like. On the other hand, mortar is obtained by kneading a binder, water, fine aggregate, admixture and the like. The composition of each material constituting the concrete and mortar is appropriately determined so as to ensure the necessary strength and workability.
For example, Ultra High Strength Fiber Reinforced Concrete (UFC) has a low water binder ratio and contains fibers for the purpose of ensuring high strength, proof stress and toughness. (For example, refer to Patent Document 1). Ultra-high-strength fiber reinforced concrete or ultra-high-strength fiber reinforced mortar (hereinafter simply referred to as “ultra-dense cement composition”) is dense and exhibits high strength. In addition, it is possible to construct a structure excellent in water-stopping property.

Since the super dense cement composition described in Patent Document 1 requires steam heat curing, it is difficult to adopt for local production and construction, and is generally used for precast members by factory production or the like. . On the other hand, if an ultra-dense cement composition can be locally produced, it is possible to construct a structure having excellent durability and to reduce the weight by reducing the thickness of the member.
Therefore, Patent Document 2 discloses a so-called mortar composition containing cement, silica fume, water, water reducing agent, antifoaming agent, expansion material, fine aggregate, and high-tensile fiber, An ultra-compact cement composition that can express high compressive strength at an early stage by curing alone and that can reduce self-shrinkage strain is disclosed. The mortar composition of Patent Document 2 was manufactured by first mixing materials other than water, a water reducing agent and high-tensile fiber, then adding water and a water reducing agent, and kneading with a mixer to produce a mortar. Manufactured by adding high-strength fibers to mortar and further kneading.

JP 2006-298679 A JP 2012-144404 A

  However, if the aggregate is contained in the ultra-dense cement composition having a low water binder ratio, it is difficult to manage the water binder ratio, and it takes time to control the quality during production. That is, when a dry material is used as the aggregate, the aggregate absorbs moisture, so that the moisture in the cement-based composition is insufficient, and the hydration reaction may be insufficient. On the other hand, when the aggregate is used in a wet state, there is a possibility that the required strength cannot be ensured due to an increase in moisture than the design value. Moreover, when fibers are added to a cement paste that does not contain aggregates, the fibers may not be evenly dispersed. If the fiber dispersion is not uniform, the denseness may be reduced.

  From such a point of view, the present invention provides an ultra-dense cement composition in which fibers can be uniformly dispersed and a more dense super-dense cement composition having low air permeability can be produced. It is an object to propose a manufacturing method.

The present invention for solving the above problems, a cement which is added 1 m ³ per 1000kg or more, and silica fume was added 1 m ³ per 90kg or more, the limestone filler is added 1 m ³ per 280kg or more, 1 m ³ per 300kg~ 480 kg of reinforcing fiber added, water added at a ratio of 8% by mass or more with respect to 100% by mass of the binder including the cement, the silica fume and the limestone filler, and 100% by mass of the binder A super dense cement obtained by mixing a water reducing agent added at a rate of 0.3% by mass or more and an antifoaming agent added at a rate of 0.1% by mass or more with respect to 100% by mass of the binder. It is a manufacturing method of a composition. The method for producing the ultra-dense cement composition includes a first mixing step in which a half amount of the reinforcing fiber, the cement, the silica fume, and the limestone filler are kneaded to form a powder mixture, and the powder mixture A second mixing step in which the water, the water reducing agent, and the antifoaming agent are added and kneaded to form a cement-based matrix; and the remaining amount of the reinforcing fibers is added to and mixed with the cement-based matrix. A mixing process is performed in order.

  The reinforcing fiber preferably has a diameter in the range of 0.05 mm to 0.30 mm and a length in the range of 0.05 mm to 25 mm. According to such a method for producing an ultra-dense cement composition, the reinforcing fibers are supplied in two portions, so that the fibers can be uniformly dispersed in the material. That is, in the first mixing step, half of the reinforcing fibers can be evenly dispersed in the powder mixture. Therefore, the remaining amount is added to the cement-based matrix in which the reinforcing fibers are uniformly dispersed in the third mixing step. By adding the reinforcing fibers, the newly added reinforcing fibers can be evenly dispersed. As a result, it is possible to produce a cement composition having low air permeability and having the fibers uniformly dispersed as compared with the case where the reinforcing fibers are added after the cement matrix is formed.

  According to the method for producing a super dense cement composition of the present invention, it becomes possible to produce a denser super dense cement composition.

It is a flowchart of the manufacturing method of the ultra-dense cement composition of this embodiment. It is a perspective view which shows the test body in the experiment which investigates air permeability. It is a perspective view which shows the formwork for shape | molding a test body in the experiment which investigates air permeability. It is a perspective view which shows the other formwork for shape | molding a test body in the experiment which investigates air permeability. It is a top view which shows the cross section of the test body in the experiment which investigates dispersibility. It is a figure which shows an example of the picked-up image in the experiment which investigates dispersibility.

  In an embodiment of the present invention, a method for producing an ultra-dense cement composition for producing a cement-based repair material (ultra-dense cement composition) used for repair work (including reinforcement work) of an existing concrete structure Will be described.

  The cement-based repair material is made by mixing at least a cement paste containing water, a water reducing agent, an antifoaming agent, a thixotropic agent, and a hardener to a binder made of cement, silica fume, and limestone filler, and reinforcing fibers. . That is, the cement-based repair material does not contain aggregate, and is not so-called fiber reinforced concrete or fiber reinforced mortar. In addition, you may add an expansion | swelling material, a setting retarder, a synthetic resin powder, a polymer emulsion, a polymer dispersion etc. to a cement paste as needed.

Ordinary Portland cement is used as the cement. The cement is not limited to ordinary Portland cement. For example, when early strength development is required, early-strength Portland cement or ultra-early-strength Portland cement can be used. The cement is added in an amount of 1000 kg or more per 1 m ³ of the mixture (cement-based repair material), preferably in the range of 1000 to 1400 kg, more preferably in the range of 1100 to 1350 kg, and even more preferably in the range of 1200 to 1280 kg. To do. When the added amount of cement is less than 1000 gk per 1 m ^{3 of} the mixture, there is a possibility that sufficient blocking performance of deterioration factors cannot be secured.

As the silica fume, a glassy silica spherical ultrafine particle powder having a diameter of about 0.1 to 0.2 μm is used. In addition, the material which comprises a silica fume is not limited. Silica fume contributes to improving the strength and durability of the cement-based repair material after curing, and is effective in improving the construction (during kneading) of the cement-based repair material by controlling the low water powder ratio. Silica fume is added in an amount of 90 kg or more, preferably 90 to 280 kg, more preferably 120 to 250 kg, and still more preferably 130 to 180 kg per 1 m ³ of the mixture. Silica fume is preferably added within a range of 5 to 20% by mass with respect to 100% by mass of cement. Here, when the addition amount of silica fume is less than 90 kg per 1 m ^{3 of} the mixture, the viscosity and material separation resistance are lowered, and predetermined fluidity cannot be secured.

As the limestone filler, limestone powder having a density of about 2.7 to 2.8 g / cm ³ and a CaO (calcium oxide) component of 50% or more is used. By adding limestone filler, the voids in the cement-based repair material are filled and the compactness is improved, the initial strength is improved by promoting the hydration reaction, and cracking is less likely to occur by preventing bleeding. Become. In addition, the material added as a limestone filler is not limited, For example, you may use the heavy calcium carbonate which passes a 200 mesh (74 micron) sieve 85% or more by purity 95% or more. The limestone filler is added in an amount of 280 kg or more per 1 m ³ of the mixture, preferably in the range of 280 to 580 kg, more preferably in the range of 340 to 520 kg, and still more preferably in the range of 400 to 460 kg. Limestone powder has a good shape and has the effect of improving the fluidity of the cement paste. The limestone filler is desirably added in an amount of 28 to 35% by mass with respect to 100% by mass of the total of cement and silica fume. In addition, when the addition amount of a limestone filler is less than 280 kg per 1 m ^{3 of} the mixture, there is a possibility that appropriate fluidity at the time of placing cannot be ensured.

  Tap water is used for water. In addition, water is not limited to tap water, For example, you may use what purified river water, groundwater, etc. The water / binder ratio is 8% by mass or more, preferably 8-30% by mass, from the viewpoint of fluidity, separation resistance, strength after curing and durability. If the water / binder ratio is less than 8% by mass, the material (cement-based repair material) may not be kneaded.

  As the water reducing agent, lignin type, naphthalene sulfonic acid type, melanin type, polycarboxylic acid type, AE water reducing agent, high performance water reducing agent, high performance AE water reducing agent can be used. The amount of water reducing agent added is 0.3% by mass or more, preferably 0.3 to 100% by mass with respect to 100% by mass of the cement-based repair material in consideration of fluidity, separation resistance, strength after hardening, and compactness. It shall be in the range of 8.0 mass%.

  Examples of the antifoaming agent include phosphoric ester, silicon, polyalkylene glycol, and polyoxyalkylene. The addition amount of the defoaming material is 0.1% by mass or more, preferably 0.1 to 3.0% by mass with respect to 100% by mass of the cement-based repair material.

As the thixotropic agent, a cellulosic retarder is used. The material constituting the thixotropic agent is not limited as long as it is a material that can improve the thixotropic property of the cement-based repair material. For example, an acrylic thickener or a biopolymer thickener Other thickeners such as fiber or powder may be used. Thixotropic agent, 30 g / ^{m 3} or more with respect to the volume of the cement paste, preferably it is desirable to add at a rate of 30 to 50 g / ^{m 3.}

As the rapid hardening material (quick hardening admixture), for example, a material mainly composed of calcium aluminate, gypsum, or the like can be used. The addition amount of the rapid hardwood, scheduled curing time, temperature, depending on the season or the like, 5 kg / ^{m 3} or more with respect to the volume of the cement paste, preferably appropriately determined within a range of 5~200kg / ^{m 3} .

As the reinforcing fiber, a steel fiber having a diameter in the range of 0.05 to 0.3 mm and a length in the range of 0.05 to 25 mm is used. The reinforcing fibers are not limited to steel fibers, and for example, carbon fibers, aramid fibers, polyolefin fibers, vinylon fibers and the like may be used. The reinforcing fiber may be used in combination of steel fibers having different lengths, such as a combination of a short fiber having a length of 0.5 to 15 mm and a long fiber having a length of 10 to 30 mm. Alternatively, only steel fibers having the same length (equivalent length) may be used. The reinforcing fiber is added in the range of 300 to 480 kg / m ^{3 with} respect to the entire material. When short fibers and long fibers are used in combination, the ratio of short fibers to long fibers is preferably 1: 1, but the ratio of short fibers to long fibers is not limited.

  The cement-based repair material is manufactured in accordance with the placement timing using a mixer installed in the work yard at the construction site. As shown in FIG. 1, the method for manufacturing a cement-based repair material according to the present embodiment includes a first mixing step S1, a second mixing step S2, and a third mixing step S3. In the cement-based repair material, first, a binder composed of cement, silica fume, and limestone filler and half of the reinforcing fibers are stirred and mixed (empty kneaded) for 2 minutes or longer (first mixing step S1). In addition, although the time for emptying is not limited, it may be performed for about 2 to 5 minutes. Next, water and a liquid admixture (water reducing agent, antifoaming agent, thixotropic agent and rapid hardening material) are added and kneaded (main kneading) for 10 to 20 minutes (second mixing step S2). Then, the remaining amount (half amount) of the reinforcing fiber is added and kneaded (finished kneading) for 2 minutes (third mixing step S3). In addition, although the time of finishing kneading is not limited, Preferably it may carry out about 2 to 5 minutes.

  As described above, since the cement-based repair material of the present embodiment is kneaded by adding half of the reinforcing fibers, the cement matrix can be generated in a state where the reinforcing fibers are uniformly dispersed in advance in the powder mixture. In addition, since half of the reinforcing fibers are evenly dispersed in the cement matrix and the remaining amount of the reinforcing fibers (the remaining half) are mixed and kneaded, the reinforcing fibers are less likely to be biased. These reinforcing fibers can be kneaded in a uniformly dispersed state. That is, a cement-based material having a small air permeability coefficient after curing and excellent material separability is produced by introducing reinforcing fibers in two steps before and after the addition of water and liquid admixture. be able to.

  Further, since the cement-based repair material is a so-called cement paste that does not contain aggregates, it is easy to manage the water binder ratio. Therefore, it can be manufactured with high quality locally. Moreover, since a large-scale plant is not required, it is possible to manufacture and place a cement-based repair material even in a place where only a limited work space can be secured. Moreover, the labor and expense of carrying in from the outside can be omitted by manufacturing locally. Since cement-based repair materials do not contain aggregates, it is easy to manage (design) strength as repair materials. That is, fiber reinforced concrete and fiber reinforced mortar may cause variations in strength between the aggregate portion and the paste portion, but the cement-based repair material can ensure uniform quality as a whole. Moreover, since it does not contain aggregate, it is easy to fill even a narrow portion.

  Next, the experimental results carried out to confirm the performance of the cement composition produced by the method for producing an ultra-dense cement composition of the present invention will be described. In the experiment, half of the reinforcing fibers were added during the kneading to mix and mix the powder mixture, and the remaining amount of reinforcing fibers was added after the main kneading by adding water or a liquid admixture to the material after the kneading. A cement composition that has been added and kneaded is used. It measured about the air permeability of the hardening body formed with the cement composition, and the dispersibility of the reinforcing fiber in a cement composition.

(1) Air permeability The air permeability was confirmed by conducting a concrete aeration test by a torrent method on a plate-shaped test piece of 3 days of age formed with a cement composition. The torrent method is a test method for calculating an air permeability coefficient from a change in internal atmospheric pressure when a chamber is installed on the surface of concrete and the inside of the chamber is set to a negative pressure. In this experiment, as shown in FIG. 2, a test body 1 having a length of 30 cm, a width of 30 cm, and a thickness of 2 cm was formed, and five measurement points of the test body 1 (the center 1a of the test body 1, the upper left 1b, the upper right 1c, the lower left) In 1d and lower right 1e), the air permeability coefficient was measured. As shown in FIG. 3, the test was performed by placing a cement composition on a flat-shaped mold 2 (length 30 cm × width 30 cm × depth 2 cm) (Example 1-1) and As shown in FIG. 4, each of the specimens (Examples 1-2) formed by placing the cement composition with a vertically placed mold 3 (length 30 cm × width 2 cm × depth 30 cm), respectively. went. In addition, as a comparative example, the same test was performed on a cement composition manufactured by adding a reinforcing fiber to a cement matrix generated by the main kneading without adding the reinforcing fiber during empty kneading ( Comparative Example 1-1 and Comparative Example 1-2) were performed. The test results are shown in Table 1.

As shown in Table 1, the average value of Example 1-1 when a cement composition was placed on a flat-shaped mold 2 was 0.0027 × 10 ⁻¹⁶ m ² , a comparative example. The average value of 1-2 was 0.0051 × 10 ⁻¹⁶ m ² . Moreover, the average value of Example 1-2 at the time of placing with respect to the vertical formwork 3 is 0.0056 × 10 ⁻¹⁶ m ^2, whereas the average value of Comparative Example 1-2 is 0.0126. × 10 ⁻¹⁶ m ² . Therefore, it was confirmed that a dense cement composition having low air permeability could be produced by adding half of the reinforcing fibers during empty kneading and adding the remaining half of the reinforcing fibers after the main kneading.

(2) Dispersibility Next, a photograph of the cut surface 4 of the specimen made of the cement composition produced by the method for producing an ultra-dense cement composition of the present invention was taken, and the photographed image (see FIG. 6) Then, the area ratio occupied by the reinforcing fibers was calculated by image analysis. In this experiment, the dispersibility of each of the three specimens (Examples 2-1, 2-2, and 2-3) was measured. Further, the dispersibility measurement (photographing) was performed at five locations (upper left 4a, lower left 4b, lower right 4c, upper left 4d, center 4e) of the cut surface 4 of each specimen as shown in FIG. . And the average value and standard deviation of the ratio of the area of the reinforcing fiber of each specimen were calculated. In addition, as a comparative example, three specimens (compared with a cement composition manufactured by adding a reinforcing fiber later to a cement matrix produced by the main kneading without adding the reinforcing fiber at the time of empty kneading (comparison) Examples 2-1, 2-2, 2-3) were prepared, and the same test was performed on each specimen. The test results are shown in Table 2.

  As shown in Table 2, the standard deviation of the example was 2.56, while that of the comparative example was 1.34. Therefore, it was confirmed that the reinforcing fibers were dispersed by adding half of the reinforcing fibers during empty kneading and adding the remaining half of the reinforcing fibers after the main kneading.

The embodiment according to the present invention has been described above. However, the present invention is not limited to the above-described embodiment, and the above-described components can be appropriately changed without departing from the spirit of the present invention.
For example, the material produced by the method for producing an ultra-dense cement composition of the present invention is not limited to a cement-based repair material, and may be used, for example, as a covering material for a new structure. In addition, the use of cement-based repair materials is not limited. For example, roads, bridges, harbor structures, river structures (bank protection, piers, etc.), underground structures (tunnels, box culverts, etc.), dams, etc. It may be used for repair.

DESCRIPTION OF SYMBOLS 1 Test body 2,3 Formwork 4 Cut surface S1 1st mixing process S2 2nd mixing process S3 3rd mixing process

Claims (2)

And cement which is added 1 m ³ per 1000kg or more,
And silica fume which is added 1 m ³ per 90kg or more,
A limestone filler was added 1 m ³ per 280kg or more,
A reinforcing fiber added with 300 kg to 480 kg per 1 m ³ ;
Water added at a ratio of 8% by mass or more with respect to 100% by mass of the binder containing the cement, the silica fume and the limestone filler;
A water reducing agent added at a ratio of 0.3% by mass or more with respect to 100% by mass of the binder;
An antifoaming agent added at a ratio of 0.1% by mass or more with respect to 100% by mass of the binder, and a method for producing a super dense cement composition,
A first mixing step in which a half amount of the reinforcing fiber, the cement, the silica fume, and the limestone filler are kneaded to form a powder mixture;
A second mixing step of adding the water, the water reducing agent and the antifoaming agent to the powder mixture and kneading to produce a cementitious matrix;
A method for producing an ultra-dense cement composition, comprising sequentially performing a third mixing step of adding and mixing the remaining amount of the reinforcing fibers to the cement matrix.   The diameter of the reinforcing fiber is within a range of 0.05 mm to 0.30 mm, and the length of the reinforcing fiber is within a range of 0.05 mm to 25 mm. A method for producing a dense cement composition.