Powdered quick-setting material and concrete material

Abstract

To provide a powdered quick-setting material capable of exhibiting high long-term strength when incorporated into a concrete composition and improving workability during application.SOLUTION: A powdered quick-setting material to be incorporated into a concrete composition, the material containing, as chemical components, 30-60 mass% of CaO, 8-30 mass% of Al2O3, and 20-50 mass% of SO3, wherein an alkali content R2O (R represents an alkali metal) is 1 mass% or less, and a water-to-cement ratio (W / C) in the concrete composition is 35% or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a powder quick-setting material and a concrete material. [Background technology]

[0002] BACKGROUND ART Conventionally, in order to prevent the collapse of exposed natural ground during tunnel excavation or the like, a shotcrete method using quick-setting shotcrete in which an accelerator is mixed into concrete has been adopted.

[0003] This spraying method typically involves preparing the sprayed concrete in a measuring and mixing plant for cement, aggregate, and water installed at the excavation site, transporting it with an agitator truck, pumping it out with a concrete pump, and mixing it with an accelerated setting agent pumped in from the other side at a confluence pipe installed along the way.Then, the quick-setting sprayed concrete is sprayed onto the ground surface to a specified thickness.

[0004] The quick-setting admixtures used in the spraying method can be broadly classified into two types: powdered quick-setting admixtures whose main ingredients are calcium aluminate or alkali metal aluminate, and liquid quick-setting admixtures whose main ingredients are alkali metal aluminate or aluminum sulfate.

[0005] Powdered quick-setting admixtures are typically added in amounts ranging from 5 to 12% because they are mixed by air transport. However, when the powdered quick-setting admixture is pumped with compressed air and mixed with the shotcrete concrete, some of the powdered quick-setting admixture can scatter as dust into the work space. Therefore, there is a demand for a construction method that provides sufficient quick-setting power with low addition amounts, reduces dust and rebound, and is easy to work with.

[0006] As a construction method that generates less dust, a method has been proposed in which a powdered quick-setting admixture is made into a slurry with water or a liquid quick-setting admixture and then added to and mixed with cement concrete (see Patent Documents 1 and 2).

[0007] Furthermore, Patent Document 3 proposes a spraying material containing a slurry-like quick-setting agent obtained by mixing a powder admixture containing alkaline earth metal carbonate, calcium aluminate, alkali metal sulfate, and calcium sulfate with a liquid quick-setting agent, and a spraying method using the same. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-031166 [Patent Document 2] Japanese Patent Application Publication No. 10-317671 [Patent Document 3] International Publication No. 08 / 056716 Summary of the Invention [Problem to be solved by the invention]

[0009] However, the methods described in Patent Documents 1 and 2 are disadvantageous in terms of reducing the decrease in strength of shotcrete because the water / cement ratio increases. Furthermore, Patent Document 3 describes high quick-setting properties, but does not consider further improving long-term strength.

[0010] In view of the above, an object of the present invention is to provide a powder quick-setting material that can exhibit high long-term strength when blended into a concrete composition and can improve workability during construction. [Means for solving the problem]

[0011] The present inventors have conducted various investigations to solve the above problems, and as a result have found that the problems can be solved by the invention described below, which has led to the completion of the present invention.

[0012] [1] A powder quick-setting material to be mixed into a concrete composition, which contains, as chemical components, 30 to 60 mass% of CaO, 8 to 30 mass% of Al2O3, and 20 to 50 mass% of SO3, the alkali content of RO (R is an alkali metal) is 1 mass% or less, and the water-cement ratio (W / C) in the concrete composition is 35% or less. [2] The powder quick-setting material according to [1], which is mixed into the concrete composition together with a liquid quick-setting material. [3] The powder quick-setting material according to [1] or [2], wherein the volume-based cumulative 50% diameter (D50) is 1 to 10 μm, and the ratio (D90-D10) / D50, where D90 is the cumulative 90% diameter and D10 is the cumulative 10% diameter, is 0.7 to 1.2. [4] The powder quick-setting material according to [2] or [3], wherein the liquid quick-setting material contains aluminum sulfate as a quick-setting component. [5] The powder quick-setting material according to any one of [2] to [4], wherein the proportion of the quick-setting component in the liquid quick-setting material relative to 100 parts by mass of cement in the concrete composition is 8 parts by mass or less, and the quick-setting component in the liquid quick-setting material is 6 parts by mass or less. [6] A concrete material obtained by blending a powder quick-setting material according to any one of [1] to [5] and a liquid quick-setting material in a concrete composition. [7] The concrete material according to [6], wherein the liquid quick-setting material contains aluminum sulfate as a quick-setting component. [8] The concrete material according to [6] or [7], which is obtained by blending 8 parts by mass or less of the powder quick-setting additive and 6 parts by mass or less of the quick-setting component in the liquid quick-setting additive with respect to 100 parts by mass of cement in the concrete composition. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a powder quick-setting material that can exhibit high long-term strength when blended into a concrete composition and can improve workability during construction. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, one embodiment of the present invention (the present embodiment) will be described in detail. [Powder rapid setting material] The powder quick-setting material according to this embodiment is blended into a concrete composition, and contains, as chemical components, 30-60 mass% CaO, 8-30 mass% Al2O3, and 20-50 mass% SO3, with an alkali content of 1 mass% or less R2O (R is an alkali metal). Since the water-cement ratio (W / C) in the concrete composition is 35% or less, it is possible to exhibit high long-term strength, and blending it with a liquid quick-setting material can improve workability during construction (e.g., reduced rebound and / or dust).

[0015] As described above, the powder quick-setting material contains, as chemical components, 30 to 60 mass % of CaO, 8 to 30 mass % of Al2O3, and 20 to 50 mass % of SO3. The powder quick-setting material preferably contains 40 to 50 mass% of CaO, more preferably 43 to 48 mass% of Al2O3, preferably 10 to 28 mass% of Al2O3, more preferably 12 to 27 mass% of Al2O3, and preferably 2 to 44 mass% of SO3, more preferably 22 to 42 mass% of SO3. The amounts of chemical components in the powder quick-setting material can be determined by fluorescent X-ray measurement.

[0016] The alkali content R2O (R is an alkali metal, preferably Na or K) of the powder quick-setting material is 1% by mass or less, preferably 0.9% by mass or less, and more preferably 0.85% by mass or less. If the alkali content exceeds 1 mass %, it becomes difficult to obtain high long-term strength.

[0017] Here, the alkali content R2O means the total amount of Na2O and K2O, and is calculated by the following formula: R2O=Na2O+0.658K2O The amount of each alkali, such as Na2O and K2O, can be determined by fluorescent X-ray measurement.

[0018] The total amount of CaO, Al2O3, and SO3 in the chemical components of the powder quick-setting material is preferably 80 mass% or more, and more preferably 90 mass% or more, from the viewpoint of more easily achieving good long-term strength development.

[0019] In the powder quick-setting material, the cumulative 50% diameter (D50) on a volume basis is 1 to 10 μm, and when the cumulative 90% diameter is D90 and the cumulative 10% diameter is D10, the ratio (D90-D10) / D50 is preferably 0.7 to 1.2. By being in the above range, the long-term strength can be increased more efficiently.

[0020] In particular, when (D90-D10) / D50 is close to 1, there will be many particles near D50. In other words, if all the particles are near D50, there will not be a wide range of particles of various sizes, which means that the hydration reaction will tend to proceed more uniformly, and long-term strength will likely increase more efficiently.

[0021] D50 is more preferably 5 to 8 μm, and even more preferably 3 to 7 μm. (D90−D10) / D50 is more preferably 0.6 to 1.5, and even more preferably 0.8 to 1.0. D10, D50, and D90 can be determined by measuring with a particle size distribution analyzer using the laser diffraction / scattering method (for example, the HORIBA LA-920 manufactured by Horiba, Ltd.) The volume-based cumulative percentage is calculated by accumulating from the finest particles to calculate D10, D50, and D90.

[0022] (liquid quick-setting agent) The liquid quick-setting admixture according to this embodiment contains aluminum sulfate as a quick-setting component. By including aluminum sulfate as a quick-setting component, the liquid quick-setting admixture is less likely to become alkaline, and as a result, it is possible to improve handleability and reduce environmental impact while maintaining good quick-setting properties. Here, the "quick-setting component" refers to the solid content of the quick-setting agent in the liquid quick-setting material.

[0023] The content (by mass) of aluminum sulfate in the quick-setting admixture components of the liquid quick-setting admixture is preferably 50 mass% or more, more preferably 80 mass% or more, and even more preferably 90 mass% or more, and it is particularly preferred that the quick-setting admixture component is aluminum sulfate alone. Examples of the quick-setting admixture component other than aluminum sulfate include polyaluminum chloride, ferric chloride, ferrous sulfate, and polyferric sulfate.

[0024] The pH of the liquid quick-setting admixture is preferably 7 or less, and more preferably 5 or less. A pH of 7 or less can exert an effect of reducing environmental impact. The pH is preferably 2 or more. The pH can be measured at 25°C using a commercially available pH meter.

[0025] The content of the quick-setting component in the liquid quick-setting admixture is preferably 20 to 40% by mass, more preferably 25 to 30% by mass. In particular, by containing 25 to 30% by mass of the quick-setting component, it is possible to improve handling properties and reduce environmental impact while maintaining good quick-setting properties. Water can be used as the liquid component that dissolves or disperses the quick-setting component.

[0026] (Concrete composition) The concrete composition according to this embodiment contains cement, fine aggregate, coarse aggregate, and water.

[0027] Examples of cement include various types of Portland cement, such as ordinary, early-strength, extra-early-strength, low-heat, and medium-heat; various mixed cements in which blast furnace slag, fly ash, or silica is mixed with these Portland cements; filler cements in which limestone powder or ground, slowly cooled blast furnace slag slag powder is mixed; and environmentally friendly cements (ecocements) produced using municipal waste incineration ash and sewage sludge incineration ash as raw materials.

[0028] As fine aggregate, river sand, mountain sand, sea sand, lime sand, silica sand, etc. can be used, and as coarse aggregate, river gravel, mountain gravel, lime gravel, etc. can be used, as well as crushed sand and crushed stone. The mixing ratio of fine aggregate and coarse aggregate can be the ratio used in normal concrete production.

[0029] The water-cement ratio (W / C) in the concrete composition is 35% or less, more preferably 30 to 35%, and even more preferably 33 to 35%, from the viewpoint of high long-term strength.

[0030] In this embodiment, for example, the above-mentioned liquid quick-setting material and the powder quick-setting material of the present invention can be mixed in a concrete composition and used.

[0031] For example, it is preferable to combine and mix the powder quick-setting material of the present invention and the liquid quick-setting material described above in a mixing pipe to form a slurry immediately before adding them to a concrete composition, in order to improve the mixability of each material.

[0032] [Concrete material] The concrete material according to this embodiment is prepared by blending 8 parts by mass or less of the powder quick-setting admixture of the present invention and 6 parts by mass or less of the quick-setting component of the liquid quick-setting admixture with respect to 100 parts by mass of cement in the concrete composition.

[0033] With the above concrete materials, it is possible to reduce the water-cement ratio (W / C) and increase the long-term strength.

[0034] The powder quick-setting admixture of the present invention is preferably 8 parts by mass or less, more preferably 3 to 8 parts by mass, and even more preferably 4 to 6 parts by mass, per 100 parts by mass of cement. The quick-setting component in the liquid quick-setting admixture described above is preferably 6 parts by mass or less, more preferably 0.4 to 3.2 parts by mass, and even more preferably 0.8 to 2.4 parts by mass, per 100 parts by mass of cement. By setting the respective proportions within the above ranges, it becomes easier to achieve both long-term strength and workability.

[0035] In the concrete material according to this embodiment, the water-cement ratio (W / C) in the concrete composition is preferably 35% or less, more preferably 30 to 35%, and even more preferably 33 to 35%, from the viewpoint of high long-term strength. [Example]

[0036] The present invention will be explained in more detail below by way of experimental examples, but the present invention is not limited to these examples.

[0037] (Powder rapid setting material) Calcium carbonate (reagent) and alumina (reagent) were melted in an electric furnace, then rapidly cooled and crushed. This was mixed with calcium sulfate (anhydrous, reagent) and sodium carbonate (reagent) to produce a powder quick-setting material with the chemical components in the proportions shown in Table 1.

[0038] (liquid quick-setting agent) A commercially available aqueous aluminum sulfate solution (solid content of aluminum sulfate: 27% by mass) was used as the liquid quick-setting agent.

[0039] (Concrete composition) Cement (commercially available, ordinary Portland cement, density 3.15 g / cm 3 ) 100 parts by mass, fine aggregate (river sand from the Himekawa River system in Niigata Prefecture, density 2.61 g / cm 3 ) and 117 parts by mass of coarse aggregate (No. 6 crushed stone from Itoigawa, Niigata Prefecture, maximum dimension 15 mm, density 2.67), and then water was added to obtain the water-cement ratio (W / C) shown in Table 1 to prepare a concrete composition.

[0040] (Compression strength evaluation) The prepared concrete composition was pumped using a concrete pump "Shintech MKW-25MT" (pumping speed: 10 m 3A Y-shaped mixing pipe was installed midway through the pressure-transport pipe, and powdered quick-setting materials and liquid quick-setting agents were added to the concrete composition by pressure transport to form concrete materials, which were then sprayed onto the wall of a mock tunnel made in the shape of an arch made of steel plates, measuring 4.4 m high and 5.5 m wide. The quick-setting components of the powder quick-setting material and liquid quick-setting admixture were mixed with 100 parts by mass of cement in the concrete composition in the proportions shown in Table 1, and the compressive strength was measured at 1 day and 28 days (measured in accordance with JIS A 1107). The results are shown in Table 1.

[0041] (Evaluation of dust amount and rebound rate) The amount of dust was measured at a position 5 m from the spraying location using a dust meter (Shibata Chemical Co., Ltd., measurement range 0.01 to 100 mg / m 3 Measurement was performed using a LD-5R type.

[0042] At the same time as measuring the amount of dust, the rebound rate when the concrete material was sprayed onto the simulated tunnel wall surface described above was calculated using the following formula. Rebound rate = (amount of concrete material that fell without adhering to the simulated tunnel) / (amount of concrete material sprayed into the simulated tunnel) x 100 (%)

[0043] [Table 1] [Industrial Applicability]

[0044] The present invention is particularly suitable for use in powder quick-setting materials used in the fields of civil engineering and construction.

Claims

1. A powder quick-setting material to be mixed into a concrete composition, which contains, as chemical components, 30 to 60 mass % of CaO, Al ２ O ３ 8 to 30 mass% of SO ３ and the alkali content R ２ 1. A powder quick-setting material, comprising: a powder quick-setting material containing 1% by mass or less of O (R is an alkali metal); and a water-cement ratio (W / C) in the concrete composition being 35% or less.

2. 2. The powder quick-setting material according to claim 1, which is mixed into the concrete composition together with a liquid quick-setting material.

3. The powder quick-setting material according to claim 1, wherein the volume-based cumulative 50% diameter (D50) is 1 to 10 μm, and the cumulative 90% diameter is D90 and the cumulative 10% diameter is D10, and the ratio (D90-D10) / D50 is 0.7 to 1.

2.

4. 3. The powder quick-setting material according to claim 2, wherein the liquid quick-setting material contains aluminum sulfate as a quick-setting component.

5. 3. The powder quick-setting material according to claim 2, wherein the proportion of the quick-setting component in the liquid quick-setting material relative to 100 parts by mass of cement in the concrete composition is 8 parts by mass or less, and the quick-setting component in the liquid quick-setting material is 6 parts by mass or less.

6. A concrete material comprising a powder quick-setting material according to any one of claims 1 to 5 and a liquid quick-setting material blended in a concrete composition.

7. 7. The concrete material according to claim 6, wherein the liquid quick-setting material contains aluminum sulfate as a quick-setting component.

8. 8. The concrete material according to claim 7, wherein the powder quick-setting material is mixed in an amount of 8 parts by mass or less and the quick-setting component in the liquid quick-setting material is mixed in an amount of 6 parts by mass or less per 100 parts by mass of cement in the concrete composition.

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