Expansion material and cement concrete

Abstract

Provided is an expansion material which has an L value of not less than 70 in a Lab color space, said expansion material comprising, as chemical components, CaO, SO3, and Al2O3, the total content of which is preferably not less than 90 mass%, and comprising, as the mineral composition thereof, CaO, CaSO4, and ye'elimite, the total content of which is preferably not less than 90 mass%.

Description

Expansion agent and cement concrete

[0001] The present invention relates to an expansive material and cement concrete.

[0002] Reducing cracking in concrete is important from the perspectives of reliability, durability, and aesthetics of civil engineering structures. Therefore, further technological advancements in expansive materials that can improve these aspects are desired.

[0003] Commonly known expansive materials include free lime-hauyne-anhydrous gypsum-based expansive materials and free lime-calcium silicate-anhydrous gypsum-based expansive materials. Recently, high-performance expansive materials that can reduce concrete cracking with smaller amounts than conventional materials have also been developed (see, for example, Patent Documents 1 and 2).

[0004] Japanese Patent Publication No. 07-232944 Japanese Patent Publication No. 2002-226243

[0005] In recent years, the use of expansive materials to suppress cracking has increased not only in the civil engineering field but also in various concrete structures and products, including those in the architectural field.

[0006] As expansive materials are applied to a variety of uses, attention is increasingly being paid to the color and appearance of concrete. For example, there is a growing demand for concrete with high whiteness, and in this case, having an expansive material that not only has a high expansion rate but also high whiteness would be highly significant as it would allow us to meet this demand.

[0007] Based on the above, the present invention aims to provide an expandable material that has high whiteness and good expansion performance.

[0008] As a result of diligent research to solve the above problems, the inventors have come up with the following invention and found that it can solve the problems. That is, the present invention is as follows.

[0009] [1] An expanding agent having an L value of 70 or higher in the Lab color space. [2] Chemical components: CaO, SO ３ Al ２ O ３The expanding agent according to [1], which contains the following, and the total content of these is 90% by mass or more. [3] As a mineral composition, CaO, CaSO ４ An expansive material according to [1] or [2], which contains E-rimite, and the total content of these is 90% by mass or more. [4] Cement concrete comprising an expansive material according to any one of [1] to [3] and cement.

[0010] According to the present invention, it is possible to provide an expandable material that has high whiteness and good expansion performance.

[0011] One embodiment of the present invention will be described in detail below.

[0012] [Expanding Agent] The expanding agent according to this embodiment has an L value of 70 or higher in the Lab color space. An L value of 70 or higher allows for an expanding agent with high whiteness. Furthermore, by incorporating it into cement concrete, it can exhibit good expansion performance. Moreover, when used in white concrete, it can reduce shrinkage while maintaining the whiteness of the white concrete, thereby improving its appearance and durability.

[0013] To achieve an L value of 70 or higher, a high-purity material should be used when preparing the expansion agent. The higher the purity, the higher the L value can be. An L value of 80 or higher is preferable, and 90 or higher is more preferable. The L value can be measured by the method described in the examples.

[0014] In the expansion material according to this embodiment, the a value in the Lab color space is preferably -1 to 2, and the b value is preferably 1 to 15.

[0015] In the expansive material of this embodiment, the chemical components are CaO, SO ３ Al ２ O ３ It contains the following, and preferably the total content of these is 90% by mass or more, more preferably 95% by mass or more, and even more preferably 98% by mass or more. When the total content is 90% by mass or more, it exhibits excellent expansion performance and can increase whiteness. The chemical composition can be measured by fluorescent X-ray analysis.

[0016] As a chemical component, CaO is preferably 40 to 80% by mass, more preferably 50 to 70% by mass, from the viewpoint of expansion performance. SO ３ is preferably 13 to 50% by mass, more preferably 20 to 35% by mass, from the viewpoints of appropriate control of expansion performance and reaction time. Further, Al ２ O ３ is preferably 1 to 20% by mass, more preferably 5 to 15% by mass, from the viewpoint of appropriate control of reaction time.

[0017] Further, the expansive agent according to the present embodiment contains, as a mineral composition, CaO, CaSO ４ , and ettringite, and the total content thereof is preferably 90% by mass or more, more preferably 93% by mass or more, and still more preferably 95% by mass or more. When the total content is 90% by mass or more, excellent expansion performance can be exhibited and the whiteness can be increased. The mineral composition can be measured by powder X-ray diffraction Rietveld analysis. Also, based on the obtained results of the chemical components, the mineral amount can be determined by calculation.

[0018] As the mineral composition, CaO is preferably 10 to 60% by mass, more preferably 20 to 50% by mass, from the viewpoint of expansion performance. CaSO ４ is preferably 15 to 60% by mass, more preferably 30 to 55% by mass, from the viewpoints of appropriate control of expansion performance and reaction time. Further, ettringite is preferably 1 to 35% by mass, more preferably 5 to 30% by mass, from the viewpoint of appropriate control of reaction time.

[0019] Further, the Blaine specific surface area of the expansive agent according to the present embodiment is preferably 2,000 to 7,000 cm ２ / g, more preferably 3,000 to 4,000 cm ２ / g, from the viewpoint of obtaining good expansion characteristics. In this specification, the Blaine specific surface area is determined in accordance with JIS R 5201 (Physical test methods for cement).

[0020] The expansive materials described above can be used as is for various purposes or mixed with other materials, but it is preferable that they be mixed into cement concrete.

[0021] [Cemented Concrete] The cemented concrete according to this embodiment includes the expansive agent of the present invention and cement. In this embodiment, cemented concrete refers collectively to cement, cement paste, mortar, and concrete.

[0022] The content of the expansive agent of the present invention is preferably 3 to 15 parts by mass, and more preferably 5 to 12 parts by mass, per 100 parts by mass of cement in the cement concrete. By setting the content to 3 to 15 parts by mass, cracking of the hardened cement can be reduced.

[0023] The cement used in this embodiment is not particularly limited and can include various types of cement such as ordinary, rapid-hardening, ultra-rapid-hardening, low-heat, and moderate-heat cements, various mixed cements obtained by mixing these cements with blast furnace slag, fly ash, silica fume, etc., environmentally friendly cements (eco-cements) manufactured using municipal solid waste incineration ash and sewage sludge incineration ash as raw materials, siliceous materials such as metakaolin and white clay calcination ash, limestone fine powder and synthetic calcium carbonate, and commercially available fine-particle cements. It is also possible to use various types of cement and various mixed cements after they have been finely powdered. Furthermore, cements that have been adjusted by increasing or decreasing the amount of components commonly used in cement (e.g., gypsum) can also be used. In this embodiment, it is preferable to select ordinary Portland cement or rapid-hardening Portland cement from the viewpoint of hydration heat, drying shrinkage, and filling properties.

[0024] Furthermore, from the standpoint of manufacturing costs and strength development, the specific surface area of ​​cement is 2,500 to 7,000 cm². ２ It is preferable that the value is / g, and the range is 2,750 to 6,000 cm². ２ It is more preferable that it be / g.

[0025] Examples of fine aggregates used in this embodiment include river sand, mountain sand, land sand, sea sand, silica sand, crushed sand, crushed limestone sand, blast furnace slag fine aggregate, and recycled fine aggregate. The type and content of the fine aggregate should be selected according to the target mechanical strength of the hardened cement concrete.

[0026] Examples of coarse aggregates used in this embodiment include crushed stone obtained by crushing andesite, rhyolite, hard sandstone, limestone, river gravel, mountain gravel, land gravel, blast furnace slag coarse aggregate, and recycled coarse aggregate. The rock type, size, and content of the coarse aggregate should be selected according to the target mechanical strength of the cement concrete hardened body.

[0027] In this embodiment, various additives may be included. Examples include water-reducing agents, air-enhancing agents, foaming agents, shrinkage-reducing agents, waterproofing agents, rust inhibitors, thickeners, polymers, water-retaining agents, pigments, water-repellent agents, efflorescence inhibitors, and the like.

[0028] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[0029] (Preparation of the expanding agent) Calcium carbonate, calcium sulfate dihydrate, and aluminum oxide were mixed so that the chemical components were in the amounts listed in Table 1. Furthermore, silicon dioxide and magnesium oxide were added as trace components to adjust the purity of the expanding agent. After mixing, the mixture was heat-treated in a small electric furnace at 1,350°C for 2 hours, left to stand at room temperature, and a Blaine value of 3,300 cm was measured using a ball mill. ２ The material was crushed to approximately [amount] / g to prepare the expansive material according to the example. The mineral composition of the prepared expansive material was measured by Rietveld analysis using powder X-ray diffraction. The results are shown in Table 1.

[0030] • Raw materials used: Calcium carbonate: Reagent grade 1, commercially available; Calcium sulfate dihydrate: Reagent grade 1, commercially available; Aluminum oxide: Reagent grade 1, commercially available; Silicon dioxide: Reagent grade 1, commercially available; Magnesium oxide: Reagent grade 1, commercially available

[0031] (Measurement of Color Difference of Expansive Material) A commercially available portable color difference meter was used to measure the color of the expansive material. The portable color difference meter was calibrated in advance using a calibration instrument so that for white, the lightness L value is 100, and the a and b values of hue and chroma are 0, and for black, all of the lightness L value and the a and b values of hue and chroma are 0. Then, the powder of the expansive material was adjusted to a flat state with a glass plate so that no unevenness occurred, and then the measuring port of the portable color difference meter was brought into contact with the powder so that the powder would not collapse, and the lightness L value and the a and b values of hue and chroma were measured.

[0032] (Measurement of Expansion Rate) 45 g of the prepared expansive material, 225 g of water, 405 g of cement, and 1350 g of fine aggregate were mixed, and a mortar composition was kneaded with a water-binder ratio of 50%. For the obtained mortar composition, based on "JIS A 6202 Test Method for Expansive Materials for Concrete", the expansion rates at 7 days and 28 days of curing were measured. Also, a comparative mortar composition was prepared in the same manner as the above mortar composition except that the cement was 450 g and no expansive material was contained, and the expansion rates at 7 days and 28 days of curing were measured in the same manner as above (Comparative Example 1). The results are shown in the table below. Considering dry shrinkage cracking, the expansion rate is preferably from 250×10 －６ to 2,000×10 －６ after 7 days, and preferably from -150×10 －６ to 0×1,500×10 －６ after 28 days.

[0033] - Materials Used Water: Tap water Cement: Ordinary Portland cement conforming to JIS R 5210:2019, commercially available product Fine aggregate: Standard sand for cement strength test conforming to JIS R 5201, commercially available product

[0034]

Claims

1. An expansive material with an L value of 70 or higher in the Lab color space.

2. Chemical components: CaO, SO ３ Al ２ O ３ The expanding material according to claim 1, which contains the following, wherein the total content of these is 90% by mass or more.

3. Mineral composition: CaO, CaSO ４ The expanding material according to claim 1, which contains E-rimite, and the total content of these is 90% by mass or more.

4. Cement concrete comprising the expansive material according to any one of claims 1 to 3 and cement.

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