Cement composition and hardened product thereof

Abstract

To provide a cement composition for neutron shielding which has high neutron shielding performance and is suitable for spraying construction and a cured product thereof.SOLUTION: A cement composition containing binder, water, coarse aggregate, fine aggregate, and special admixture, in which the coarse aggregate contains crushed olivine, and the fine aggregate contains crushed olivine sand. In cases where both the special admixture and fine aggregate contain colemanite, or in cases where only the special admixture contains colemanite, the content of colemanite is between 10 kg and 115 kg for 1 m3 of the cement composition. The total volume of crushed olivine and crushed olivine sand is between 500 L and 700 L for 1 m3 of cement composition, in cases where both special admixture and fine aggregate do not contain colemanite.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a cement composition and a hardened product thereof, and more particularly to a cement composition having neutron shielding properties and a hardened product thereof. [Background technology]

[0002] Previously, the applicant filed a patent application for an invention relating to neutron shielding concrete (Patent Document 1), in light of the fact that neutron shielding is important in shielding radiation in nuclear power-related facilities and medical facilities.

[0003] Specifically, the neutron shielding concrete of Patent Document 1 contains crushed peridotite as coarse aggregate, crushed peridotite sand and colemanite as fine aggregates, and the colemanite content is 5 to 20 mass % based on the mass of the concrete.

[0004] The neutron shielding concrete of Patent Document 1 has a compressive strength comparable to that of concrete using ordinary aggregate, and also provides excellent neutron shielding performance.

[0005] Furthermore, Patent Document 2 discloses a method for forming a neutron shielding layer with a uniform density of shielding material by pressurizing two-component urethane foam raw material into a two-hole spray gun and spraying it onto the interior walls, ceiling, and floor of a room, and then pressurizing and merging granular colemanite neutron shielding material into the outlet of the two-hole spray gun and spraying it. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-39453 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-58209 Summary of the Invention [Problem to be solved by the invention]

[0007] In facilities that measure elementary particles such as neutrinos, high sensitivity is required, and therefore experimental equipment is installed at depths of 1,000 m or more underground where rock shielding is expected to be available in order to avoid measurement noise caused by cosmic rays and natural radioactivity contained in bedrock and concrete. However, neutrons with extremely high energy originating from cosmic rays can penetrate bedrock and easily enter underground water tanks.

[0008] Furthermore, measurement noise caused by natural radioactive materials contained in the aggregates of the shotcrete and backfill concrete applied during the excavation of the underground cavern cannot be ignored. It is desirable to reduce these noises so as not to interfere with neutrino observation.

[0009] Although the neutron shielding concrete of Patent Document 1 provides excellent neutron shielding performance, it does not disclose anything about spray application. Furthermore, while the neutron shielding concrete of Patent Document 1 contains a specified amount of colemanite, the inventors' investigations revealed that the presence of colemanite in that amount delays setting, making it impossible to use the concrete as is for shotcrete, which requires rapid strength development.

[0010] Furthermore, according to the method for forming a neutron shielding layer in Patent Document 2, the resulting shielding layer is urethane foam, not concrete. Therefore, Patent Document 2 does not provide any hints as to the problem of early strength development caused by adding colemanite to a composition for spraying concrete, or how to solve it.

[0011] In view of the above problems, an object of the present invention is to provide a neutron shielding cement composition having high neutron shielding performance and suitable for spray application, and a hardened product thereof. [Means for solving the problem]

[0012] The present inventors have conducted extensive research to achieve the above object, and as a result, have found that even when the amount of colemanite is reduced compared to conventional cement compositions to ensure early strength development, the use of colemanite with a small particle size can maintain the shielding performance against neutrons originating from cosmic rays, and moreover, surprisingly, that natural radioactivity can be reduced even without the inclusion of colemanite at all, which led to the development of the present invention.

[0013] That is, the object of the present invention is to A cement composition comprising a binder, water, coarse aggregate, fine aggregate and a special admixture, The coarse aggregate contains crushed peridotite stone, the fine aggregate contains crushed peridotite sand, and when the special admixture and the fine aggregate contain colemanite, or when only the special admixture contains colemanite, the content of the colemanite is 1 / 3 of the cement composition. 3 In the case where neither the special admixture nor the fine aggregate contains colemanite, the total volume of the crushed peridotite stone and the crushed peridotite sand is in the range of 10 kg or more and less than 115 kg per cubic meter of the cement composition. 3 It has been found that this can be achieved by a cement composition characterized in that the viscosity of the cement is in the range of 530L or more and 650L or less.

[0014] Furthermore, the cement composition of the present invention preferably has a slump value measured in accordance with JIS A1101 in the range of 12 cm or more and 25 cm or less (particularly preferably 15.5 cm or more and 23.5 cm or less), and a V-funnel flow time measured in accordance with JSCE-F512 of 20 seconds or less (particularly preferably 10 seconds).

[0015] Furthermore, the cement composition of the present invention preferably contains an accelerator.

[0016] Furthermore, the above-mentioned object of the present invention can also be achieved by a hardened product of the cement composition of the present invention, in which the heated moisture content, determined by Karl Fischer titration (heating temperature: 950°C, 20 minutes), is 8% by mass or more relative to the total mass of an air-dried sample of the hardened product. [Effects of the Invention]

[0017] According to the present invention, when the special admixture and fine aggregate, or only the special admixture, contain colemanite, the content of colemanite is 3 By setting the range of 10 kg or more and less than 115 kg, it is possible to maintain the neutron shielding performance from cosmic rays while solving the problem of delayed coagulation caused by colemanite.

[0018] In addition, when neither the special admixture nor the fine aggregate contains colemanite, the total volume of the crushed peridotite stone and the crushed peridotite sand is 1 m3 of the cement composition. 3 By keeping the concentration in the range of 530L to 650L, not only is the problem of delayed coagulation caused by colemanite eliminated, but natural radioactivity can also be reduced. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 shows the neutron shielding performance of the hardened cement composition of Example 1, determined by simulation calculation. The vertical axis shows the attenuation rate per neutron from the source, and the horizontal axis shows the thickness of the hardened product. [Figure 2] FIG. 2 shows the neutron shielding performance of the hardened product of the cement composition of Example 2, determined by simulation calculation. The vertical axis shows the attenuation rate per neutron from the source, and the horizontal axis shows the thickness of the hardened product. [Figure 3] FIG. 3 shows the neutron shielding performance of the hardened cement composition of Comparative Example 1 (standard mix) determined by simulation calculation, where the vertical axis represents the attenuation rate per source neutron and the horizontal axis represents the thickness of the hardened product. DETAILED DESCRIPTION OF THE INVENTION

[0020] <Cement composition> The cement composition of the present invention comprises a binder, water, coarse aggregate, fine aggregate, and a special admixture, The coarse aggregate includes crushed peridotite stone, The fine aggregate includes crushed peridotite sand; When the special admixture and the fine aggregate contain colemanite, or when only the special admixture contains colemanite, the content of the colemanite is 1 / 3 of the cement composition. 3 The range is between 10kg and 115kg. When neither the special admixture nor the fine aggregate contains colemanite, the total volume of the crushed peridotite stone and the crushed peridotite sand is less than 1 m3 of the cement composition. 3 The range is between 530L and 650L.

[0021] [Binding material] Binder is a general term for materials that react with water to produce substances that contribute to the strength of concrete, and includes cement, ground granulated blast furnace slag, fly ash, etc.

[0022] Cement is an inorganic binder that hardens when mixed with water, and hydraulic cement is used in the present invention. As the hydraulic cement, a simple cement such as Portland cement, hydraulic lime, Roman cement, or natural cement may be used, or a mixed cement such as lime-mixed cement or mixed Portland cement may be used.

[0023] Ground granulated blast furnace slag is mixed with ordinary Portland cement to produce blast furnace cement, which has high long-term strength and is excellent at inhibiting alkali-silica reaction and salt penetration.

[0024] Fly ash is a by-product of coal ash produced when pulverized coal is burned in thermal power plants. When included in binders, it increases the fluidity of cement compositions, reduces the unit water content, and reduces the heat of hydration.

[0025] In the cement composition of the present invention, the content of the binder is 3 Preferably, the cement composition is 270 kg or more and 570 kg or less per 1 m 3 The maximum weight is between 360kg and 550kg.

[0026] [Coarse aggregate] Coarse aggregate refers to aggregate that retains 85% or more by weight on a 5 mm mesh sieve. In the present invention, the coarse aggregate preferably contains crushed peridotite. Peridotite has slightly different chemical compositions depending on its origin, but it is generally composed mainly of SiO2 and MgO and contains approximately 2 to 14% by mass of water of crystallization.

[0027] As the coarse aggregate, it is possible to use other ordinary coarse aggregates (gravel, etc.) other than crushed peridotite stone. However, in order to improve the neutron shielding performance, the total volume of crushed peridotite stone (coarse aggregate) and crushed peridotite sand (fine aggregate) described later must be less than 1 m3 of the cement composition. 3 It is preferable that the capacity is 500 L or more.

[0028] The content of coarse aggregate can be selected appropriately, but 3 The capacity is 140L or more and 510L or less, preferably 180L or more and 440L or less.

[0029] [Fine aggregate] Fine aggregate refers to aggregate that passes 100% by weight through a 10 mm mesh sieve. In the present invention, the fine aggregate preferably contains crushed peridotite sand. However, the fine aggregate may contain other ordinary fine aggregates (sand, etc.) besides crushed peridotite sand.

[0030] The fine aggregate may also contain colemanite, which is a mineral whose main component is 2CaO·3B2O3·5H2O, and preferably contains 29.50% by weight or more of B2O3.

[0031] The content of fine aggregate can be selected appropriately, but 3 The capacity is 140L or more and 510L or less, preferably 180L or more and 440L or less.

[0032] [Special admixture] The cement composition of the present invention contains colemanite powder having a particle size of 150 μm or less as a special admixture. When the special admixture and fine aggregate, or only the special admixture, contain colemanite, the content of colemanite is 1 / 3 of the cement composition.3 The content of colemanite is preferably in the range of 10 kg to 115 kg per 1 m of the cement composition. 3 The weight is between 20kg and 80kg.

[0033] When special admixture and fine aggregate, or only special admixture, contain colemanite, the content of colemanite shall be calculated based on the cement composition. 3 By setting the range of 10 kg or more and less than 115 kg, it is possible to maintain the neutron shielding performance from cosmic rays while solving the problem of delayed coagulation caused by colemanite.

[0034] Furthermore, when colemanite is contained in the cement composition of the present invention, the amount of colemanite is less than conventionally used, and therefore, from the viewpoint of ensuring the dispersibility of the colemanite in the hardened cement composition, it is preferable that only the special admixture contains colemanite (i.e., that only colemanite powder having a particle size of 150 μm or less is contained in the cement composition).

[0035] In addition, when neither the special admixture nor the fine aggregate in the cement composition of the present invention contains colemanite, the total volume of the crushed peridotite stone and the crushed peridotite sand is 1 m3 of the cement composition. 3 The range is 500L or more and 700L or less, and preferably 550L or more and 650L or less.

[0036] When neither the special admixture nor the fine aggregate in the cement composition of the present invention contains colemanite, the total volume of the crushed peridotite stone and the crushed peridotite sand is 1 m3 of the cement composition. 3 By keeping the concentration in the range of 500 L or more and 700 L or less, not only is the problem of delayed setting caused by colemanite eliminated, but natural radioactivity can also be reduced. Note that the case where neither the special admixture nor the fine aggregate in the cement composition of the present invention contains colemanite refers to the case where the cement composition of the present invention does not contain colemanite.

[0037] Furthermore, the cement composition of the present invention can contain a water-reducing agent, preferably a high-performance water-reducing agent. When a high-performance water-reducing agent is added to the cement composition, the amount of the water-reducing agent is in the range of 0.1% by weight to 5% by weight, preferably 0.4% by weight to 3.5% by weight, based on the amount (weight) of cement. Note that the water-reducing agent is not included in the total amount of the cement composition in calculations.

[0038] Furthermore, it is preferable that an accelerator is added to the cement composition of the present invention. An accelerator is one of the admixtures that adjusts the setting and hardening speed of the cement composition and is used in shotcrete. When an accelerator is added to the cement composition, it is in the range of 0.1% by weight to 20% by weight, preferably 5% by weight to 15% by weight, based on the cement blend amount (weight). Note that the accelerator is not included in the total amount of the cement composition in calculations.

[0039] The cement composition of the present invention may contain other components in addition to the binder, water, coarse aggregate, fine aggregate, special admixture, water-reducing agent, and quick-setting admixture. Examples of other components that the cement composition of the present invention may contain include well-known and commonly used additives such as fluidizing agents, antifoaming agents, foaming agents, waterproofing agents, colorants, shrinkage-reducing agents, rust inhibitors, and water-retaining agents.

[0040] The properties of the cement composition of the present invention immediately after mixing are such that the slump value measured in accordance with JIS A1101 is preferably in the range of 12 cm to 25 cm, more preferably 15.5 cm to 23.5 cm.

[0041] Furthermore, the flow time through a V-funnel measured in accordance with JSCE-F512 is preferably 20 seconds or less, and more preferably 10 seconds or less.

[0042] When the cement composition of the present invention has a slump value of 12 cm or more and 25 cm or less immediately after mixing, as measured in accordance with JIS A1101, and a V-funnel flow time of 20 seconds or less, as measured in accordance with JSCE-F512, the workability of compaction and spraying is improved, and the quality of the hardened cement composition is more reliably ensured.

[0043] <Hardened cement composition> The hardened product of the cement composition of the present invention can be obtained by hardening the cement composition.

[0044] The hardened product of the cement composition can be obtained in various shapes such as buildings, roads, dams, viaducts, tunnels, port facilities, etc., by, for example, pouring the cement composition into a formwork, compacting it, optionally finishing it, and then curing it. Note that, since the hardened product of the cement composition of the present invention has high neutron shielding performance, the hardened product of the cement composition of the present invention can be preferably used in nuclear power-related facilities, medical facilities, and facilities for measuring elementary particles such as neutrinos, particularly in facilities for measuring elementary particles such as neutrinos.

[0045] The hardened product of the cement composition may also be sprayed concrete (hardened product) obtained by applying the cement composition immediately after mixing using a special spraying machine and pumping it with compressed air. The cement composition of the present invention has a reduced colemanite content compared to conventional cement compositions, which eliminates the problem of delayed setting caused by colemanite, resulting in a well-applied sprayed concrete (hardened product), which also has high neutron shielding performance.

[0046] The hardened product of the cement composition of the present invention has a heated moisture content of 8% by mass or more, preferably 10% by mass or more, based on the total mass of an air-dried sample of the hardened product, as determined by Karl Fischer titration (heating temperature: 950°C, 20 minutes).

[0047] The sample used in the Karl Fischer titration method is a pulverized specimen for compressive strength testing.

[0048] High neutron shielding performance can be maintained by ensuring that the heated moisture content, determined by Karl Fischer titration (heating temperature: 950°C, 20 minutes), is 8% by mass or more relative to the total mass of an air-dried sample of the hardened cement composition of the present invention. This is presumably because the peridotite in the hardened product contains a large amount of crystal water, causing elastic scattering of neutrons with the hydrogen atoms in this crystal water, slowing down medium-energy neutrons; because peridotite and (if present) colemanite are both rocks and therefore contain iron, which has the effect of slowing down high-energy neutrons; and because colemanite contains boron, which absorbs the slower-energy neutrons.

[0049] In addition, in the cement composition of the present invention, when the special admixture and the fine aggregate contain colemanite, or when only the special admixture contains colemanite, the content of colemanite is 3 The colemanite content in the hardened product of the cement composition of the present invention is in the range of 0.25 mass % or more and less than 5 mass % based on the total mass of an air-dried sample of the hardened product.

[0050] The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the invention.

[0051] For example, examples of the hardened product of the cement composition include a building cast into a formwork and sprayed concrete, but the hardened product of the cement composition is not limited to these. For example, the hardened product of the cement composition may be backfill concrete that is filled between a structure and a slope. [Example]

[0052] EXAMPLES The present invention will be specifically explained below by showing examples, but the present invention is not limited to these examples.

[0053] The materials used in the examples are shown in Table 1 below.

[0054] [Table 1]

[0055] <1. Preparation of cement compositions of Examples 1 and 2 and Comparative Example 1> The composition shown in Table 2 was mixed in a 50 L nominal capacity, forced biaxial mixer, with a mixing volume of 25 L to prepare a cement composition. The mixing procedure involved first adding cement (C), fine aggregate (S), and coarse aggregate (G) to the 50 L nominal capacity, forced biaxial mixer, and mixing for 15 seconds. Then, water (W) was added and mixed for an additional 30 seconds. This mixture was scraped off, mixed for an additional 90 seconds, and then discharged to prepare a cement composition. In Example 1, the special admixture (P) was first added to the mixer together with the cement (C), etc., and the water-reducing agent (AD) was added when the water was measured.

[0056] As shown in Table 2, Comparative Example 1 is a standard mix that uses ordinary aggregate and does not contain colemanite as a special admixture. In both Examples 1 and 2, crushed peridotite stone is used as coarse aggregate and crushed peridotite sand as fine aggregate instead of ordinary aggregate. Example 1 also contains a special admixture (colemanite (powder, 150 μm or less)). In Table 2, the total amount of S(1) and G(1) in Example 1 is calculated based on the total amount of S(1) and G(1) per 1 ml of cement composition. 3 The total amount of S(1) and G(1) in Example 2 was 559 L per 1 m of cement composition. 3 It is 567L per unit.

[0057] [Table 2]

[0058] <2. Evaluation of fresh properties of cement composition> For the cement compositions (fresh concrete) prepared in <1. Preparation of cement compositions of Examples 1 and 2 and Comparative Example 1> above, the slump value was measured according to JIS A1101, the air content according to JIS A1128, the V-funnel flow time according to JSCE-F512, and the temperature of the fresh concrete (Co temperature) according to JIS A1156. The results are shown in Table 3 below.

[0059] [Table 3]

[0060] As shown in Table 3, in Example 2, in which the aggregate was replaced from Comparative Example 1 (standard mix), and in Example 1, in which a special admixture (colemanite (powder)) was added in addition to replacing the aggregate, the fresh properties were equivalent to those of Comparative Example 1 (standard mix).

[0061] <3. Evaluation of compressive strength> For each of the prepared cement compositions, hardened cement compositions with a diameter of 100 mm and a height of 200 mm were prepared, and the compressive strength at ages of 7 days and 28 days was measured in accordance with JIS A1108. The results are shown in Table 4.

[0062] [Table 4]

[0063] As shown in Table 4, the hardened products of the cement compositions of Examples 1 and 2 exhibited compressive strengths equivalent to that of Comparative Example 1 (standard mix).

[0064] <4.Moisture content> Using crushed samples of the hardened product of each cement composition prepared in the above <3. Evaluation of compressive strength>, the adhered moisture was determined by the loss on drying method at 105°C, and the heated moisture was determined by Karl Fischer titration. Here, the heated moisture refers to the total value of the bound moisture and crystalline moisture in the hardened product of the cement composition. The results are shown in Table 5.

[0065] [Table 5]

[0066] As shown in Table 5, the values ​​of heated moisture measured in the samples of Examples 1 and 2 were 10 mass % or more, which indicates that Examples 1 and 2 contain peridotite.

[0067] <5. B2O3 content> Using crushed samples of the hardened products of each cement composition prepared in the above <3. Evaluation of compressive strength>, the amount of B2O3 (wt%) in the hardened products was determined by ICP-AES. The results are shown in Table 6.

[0068] [Table 6]

[0069] As shown in Table 6, B2O3 was detected only in Example 1. B2O3 is not contained in ordinary fine aggregates or coarse aggregates, but is contained in colemanite. Therefore, by measuring B2O3, the presence of colemanite in the hardened cement composition can be confirmed.

[0070] <6. Shielding calculation results> The neutron shielding performance of the hardened cement compositions prepared in the above <3. Evaluation of compressive strength> was calculated by simulation. The calculation code used was the radiation behavior simulation code MCNP version 6.2 developed by Los Alamos National Laboratory in the United States. For nuclear data, JENDL-4.0 and JENDL-4.0 / HE prepared by the Japan Atomic Energy Agency were used.

[0071] Simulation calculations were performed for a wide range of energies (2.45 MeV, 10 MeV, 20 MeV, 100 MeV, 1 GeV), from slow neutrons typically used in nuclear facilities to fast neutrons originating from cosmic rays. The results for each are shown in Figures 1 to 3.

[0072] 1 to 3 show the attenuation rate per neutron from the radiation source. From these figures, it can be seen that the concrete of Example 1 (hardened cement composition, the same applies hereinafter) has 1.58 times the shielding performance (shielding thickness ratio required to attenuate the neutron flux to 1 / 100) against a 2.45 MeV neutron source, 1.26 times the shielding performance against a 10 MeV neutron source, and 1.23 times the shielding performance against a 20 MeV neutron source, compared to the concrete of Comparative Example 1 (standard mix). It can also be seen that the concrete of Example 2 has 1.40 times the shielding performance against a 2.45 MeV neutron source, 1.18 times the shielding performance against a 10 MeV neutron source, and 1.16 times the shielding performance against a 20 MeV neutron source, compared to the concrete of Comparative Example 1 (standard mix).

[0073] <7. Natural radioactivity amount> The amount of naturally occurring radioactivity (uranium series, thorium series, potassium 40) contained in the hardened product of each cement composition prepared in <3. Evaluation of compressive strength> above was measured using a germanium detector. The results are shown in Table 7.

[0074] [Table 7]

[0075] As shown in Table 7, when comparing the uranium series nuclides using the highest energy Pa-234m, the radioactivity of Comparative Example 1 (standard mix) was 0.12 Bq / g, but was undetectable in both Examples 1 and 2. When comparing the thorium series nuclides using the highest energy Ac-228, the radioactivity of Example 1 was 23% of that of Comparative Example 1, and 28% of that of Example 2. When comparing K-40 (potassium 40), the radioactivity of both Examples 1 and 2 was 6% of that of Comparative Example 1. Thus, it can be seen that the naturally occurring radioactivity contained in the hardened products of Examples 1 and 2 is very low compared to the hardened product of the cement composition of Comparative Example 1 with the standard mix.

Claims

1. A cement composition for spray application, comprising a binder, water, coarse aggregate, fine aggregate, and a special admixture, Only the special admixture contains colemanite, and the content of the colemanite is 1 / m of the cement composition. ３ The range is 10 kg or more and less than 115 kg, The colemanite is a colemanite powder having a particle size of 150 μm or less; A cement composition for spray application, characterized by:

2. 2. The cement composition for spray application according to claim 1, characterized in that the slump value measured in accordance with JIS A1101 is in the range of 12 cm or more and 25 cm or less, and the flow time through a V-funnel measured in accordance with JSCE-F512 is 20 seconds or less.

3. 3. The cement composition for spray application according to claim 1, further comprising an accelerated setting additive.

4. A hardened product of the cement composition for spray application according to any one of claims 1 to 3, characterized in that the amount of heated moisture determined by Karl Fischer titration (heating temperature: 950°C, 20 minutes) is 8% by mass or more relative to the total mass of an air-dried sample of the hardened product.

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