Artificial lightweight aggregate for neutron shielding and manufacturing method therefor

Abstract

The present invention relates to an artificial lightweight aggregate and, more specifically, to a carbon-reduction type artificial lightweight aggregate based on fly ash, which can be manufactured even at a low temperature. This PCT patent application has been filed with the support of "IP advancement and commercialization for the promotion of industrialization of eco-friendly construction materials of blast furnace slag-based composition and cured product technology thereof" (project number: RS-2024-00422600) under the 2024 university technology management promotion program IP star scientist support type, which is a national research and development project by the Ministry of Science and ICT of the Republic of Korea. Additionally, this PCT patent application has been filed with the support of "Enhancement of interlayer bonding strength in 3D concrete printing for construction through electrophoretic deposition technique" (project number: RS-2023-00245603) under the creative challenge research base support project by the Ministry of Education (supporting agency: National Research Foundation of Korea).

Description

Neutron shielding artificial lightweight aggregate and its manufacturing method

[0001] The present invention relates to an artificial lightweight aggregate, and more particularly, to a carbon-reducing artificial lightweight aggregate that can be manufactured at low temperatures based on fly ash.

[0002] Unlike fast neutrons, which are shielded by elastic collisions with water molecules, thermal neutrons require absorption shielding by substances with high neutron absorption cross sections, such as boron, gadolinium, samarium, and cadmium.

[0003] Among them, boron has been used a lot for economic reasons, and a lot of research has been conducted on boron compounds such as B4C, but there are difficulties in using it due to the problem of reduced concrete strength when used, difficulty in mixing in large quantities due to the price of close to 1 million won per kg, and difficulty in controlling particle size due to its characteristics.

[0004] For this reason, much research has been conducted to mix boric acid (1 kg, 2,960 won) or Borax (1 kg, 2,640 won) into concrete to secure neutron shielding performance while being economical.

[0005] However, it has been reported that these boron compounds inhibit setting and reduce compressive strength development when directly mixed into general Portland cement, and as a result, direct mixing into general concrete is practically difficult.

[0006] Accordingly, there is a need to develop a new high-strength cement-free binder that, unlike Portland cement, can contain neutron shielding materials without any problems.

[0007] When exposed to neutron radiation, the crystalline structure of aggregates becomes amorphous due to increased lattice constants and lattice defects, increasing their volume and ultimately causing severe expansion cracking in concrete. Therefore, all aggregates used in concrete in nuclear facilities are high-crystallinity natural and crushed stone aggregates, making them vulnerable to aggregate expansion and destruction by neutron radiation. Consequently, the use of amorphous aggregates is essential for concrete intended for neutron shielding.

[0008] Existing artificial lightweight aggregate technologies use kilns for high-temperature firing at over 1,200 °C, so even if neutron shielding materials are included, they are decomposed and lost during the manufacturing process. Therefore, it is virtually impossible to incorporate neutron shielding materials into existing artificial aggregates. Therefore, artificial lightweight aggregates must be manufactured and cured under low-temperature conditions so that neutron shielding materials can be maintained.

[0009] (Prior art document) Republic of Korea Patent Publication No. 10-1938528

[0010] The purpose of the present invention is to provide a construction material manufactured from coal ash (fly ash), a by-product generated from thermal power plants, etc., without using poplite cement.

[0011] In addition, the present invention provides an artificial lightweight aggregate that can be manufactured at a low temperature, does not use Portland cement, and can maintain a neutron shielding material.

[0012] The purposes of the present invention are not limited to those mentioned above, and other purposes not mentioned will be clearly understood from the description below.

[0013] A neutron shielding artificial lightweight aggregate according to one embodiment of the present invention comprises fly ash; calcium hydroxide (Ca(OH)2); sodium carbonate (Na2CO3), a boron compound, and an accelerator.

[0014] The above fly ash may contain more than half of silicon dioxide (SiO2) and aluminum oxide (Al2O3).

[0015] The above fly ash contains SiO2, Al2O3, CaO and Fe2O3, and the fly ash may have a content distributed in the order of SiO2, Al2O3, CaO and Fe2O3.

[0016] The above fly ash may be composed of SiO2, Al2O3, CaO, Fe2O3, MgO, TiO2, P2O5, K2O, Na2O, SO3, SrO, BaO, ZrO2, MnO, V2O5, ZnO, Cr2O3, CuO, NiO, Y2O3, and Ga2O3.

[0017] The fly ash may be comprised of 55 to 69 wt%, the calcium hydroxide of 20 wt%, the sodium carbonate of 10 wt%, and the boron compound of 1 to 5 wt%, and the accelerator may be comprised of 0.6 wt% based on 100 wt% of the total of the fly ash, the calcium hydroxide, and the sodium carbonate.

[0018] The above boron compound may be boric acid (H3BO3) or borax (Na2B4O7).

[0019] The above promoter is sucrose (C 12 H 22 O 11 ), sodium citrate, sodium tartrate, and sodium gluconate.

[0020]

[0021] In addition, a method for manufacturing a neutron shielding artificial lightweight aggregate according to one embodiment of the present invention comprises the steps of preparing 100 parts by weight of a mixture of fly ash; calcium hydroxide (Ca(OH)2); sodium carbonate (Na2CO3), a boron compound, and an accelerator; a first pelletizing step of adding 90 parts by weight of the mixture and 27 parts by weight of water to a disk pelletizer; a second pelletizing step of additionally adding 10 parts by weight of the mixture to the disk pelletizer; and a third pelletizing step of additionally adding 3 parts by weight of water to the disk pelletizer.

[0022] The above fly ash may contain more than half of silicon dioxide (SiO2) and aluminum oxide (Al2O3).

[0023] The above fly ash contains SiO2, Al2O3, CaO and Fe2O3, and the fly ash may have a content distributed in the order of SiO2, Al2O3, CaO and Fe2O3.

[0024] The above fly ash may be composed of SiO2, Al2O3, CaO, Fe2O3, MgO, TiO2, P2O5, K2O, Na2O, SO3, SrO, BaO, ZrO2, MnO, V2O5, ZnO, Cr2O3, CuO, NiO, Y2O3, and Ga2O3.

[0025] The above mixture may include 55 to 69 wt% of the fly ash, 20 wt% of the calcium hydroxide, 10 wt% of the sodium carbonate, and 1 to 5 wt% of the boron compound, and the accelerator may be included in an amount of 0.6 parts by weight based on 100 parts by weight of the total of the fly ash, the calcium hydroxide, and the sodium carbonate.

[0026] The above boron compound may be boric acid (H3BO3) or borax (Na2B4O7).

[0027] The above promoter is sucrose (C 12 H 22 O 11 ), sodium citrate, sodium tartrate, and sodium gluconate.

[0028] The present invention has the effect of providing an artificial aggregate based on a cement-free binder that can cure fly ash, a by-product generated from thermal power plants, at low temperatures without using a rotary kiln.

[0029] In addition, the present invention has the effect of providing a high-strength cement-free binder that does not cause problems even when containing a neutron shielding material.

[0030] In addition, the present invention has the effect of providing an artificial lightweight aggregate that can be manufactured and cured under low-temperature conditions and that can be maintained by a neutral shielding material.

[0031] The technical effects of the present invention are not limited to those mentioned above, and other technical effects not mentioned will be clearly understood by those skilled in the art from the description below.

[0032]

[0033] Figure 1a illustrates the results of particle size analysis of fly ash according to one embodiment of the present invention.

[0034] Figure 1b illustrates the results of particle size analysis of Portland cement according to one embodiment of the present invention.

[0035] Figure 2 illustrates the results of measuring the aggregate crushing rate and crushing load of artificial lightweight aggregate according to one embodiment of the present invention.

[0036] Figure 3 illustrates the results of wear rate analysis of artificial lightweight aggregate according to one embodiment of the present invention.

[0037] Figure 4 illustrates the XRD analysis results of an artificial lightweight aggregate according to one embodiment of the present invention.

[0038] Figure 5 illustrates the results of a boron elution test analysis of an artificial lightweight aggregate according to one embodiment of the present invention.

[0039] Figure 6 illustrates the results of compressive strength analysis of artificial lightweight aggregate according to one embodiment of the present invention.

[0040] Figure 7 shows the results of the compressive strength analysis of Portland cement.

[0041] Figure 8 illustrates the results of compressive strength analysis of concrete according to one embodiment of the present invention.

[0042] A neutron shielding artificial lightweight aggregate according to one embodiment of the present invention comprises fly ash; calcium hydroxide (Ca(OH)2); sodium carbonate (Na2CO3), a boron compound, and an accelerator.

[0043] The above fly ash may contain more than half of silicon dioxide (SiO2) and aluminum oxide (Al2O3).

[0044] The above fly ash contains SiO2, Al2O3, CaO and Fe2O3, and the fly ash may have a content distributed in the order of SiO2, Al2O3, CaO and Fe2O3.

[0045] The above fly ash may be composed of SiO2, Al2O3, CaO, Fe2O3, MgO, TiO2, P2O5, K2O, Na2O, SO3, SrO, BaO, ZrO2, MnO, V2O5, ZnO, Cr2O3, CuO, NiO, Y2O3, and Ga2O3.

[0046] The fly ash may be comprised of 55 to 69 wt%, the calcium hydroxide of 20 wt%, the sodium carbonate of 10 wt%, and the boron compound of 1 to 5 wt%, and the accelerator may be comprised of 0.6 wt% based on 100 wt% of the total of the fly ash, the calcium hydroxide, and the sodium carbonate.

[0047] The above boron compound may be boric acid (H3BO3) or borax (Na2B4O7).

[0048] The above promoter is sucrose (C 12 H 22 O 11 ), sodium citrate, sodium tartrate, and sodium gluconate.

[0049]

[0050] In addition, a method for manufacturing a neutron shielding artificial lightweight aggregate according to one embodiment of the present invention comprises the steps of preparing 100 parts by weight of a mixture of fly ash; calcium hydroxide (Ca(OH)2); sodium carbonate (Na2CO3), a boron compound, and an accelerator; a first pelletizing step of adding 90 parts by weight of the mixture and 27 parts by weight of water to a disk pelletizer; a second pelletizing step of additionally adding 10 parts by weight of the mixture to the disk pelletizer; and a third pelletizing step of additionally adding 3 parts by weight of water to the disk pelletizer.

[0051] The above fly ash may contain more than half of silicon dioxide (SiO2) and aluminum oxide (Al2O3).

[0052] The above fly ash contains SiO2, Al2O3, CaO and Fe2O3, and the fly ash may have a content distributed in the order of SiO2, Al2O3, CaO and Fe2O3.

[0053] The above fly ash may be composed of SiO2, Al2O3, CaO, Fe2O3, MgO, TiO2, P2O5, K2O, Na2O, SO3, SrO, BaO, ZrO2, MnO, V2O5, ZnO, Cr2O3, CuO, NiO, Y2O3, and Ga2O3.

[0054] The above mixture may include 55 to 69 wt% of the fly ash, 20 wt% of the calcium hydroxide, 10 wt% of the sodium carbonate, and 1 to 5 wt% of the boron compound, and the accelerator may be included in an amount of 0.6 parts by weight based on 100 parts by weight of the total of the fly ash, the calcium hydroxide, and the sodium carbonate.

[0055] The above boron compound may be boric acid (H3BO3) or borax (Na2B4O7).

[0056] The above promoter is sucrose (C 12 H 22 O 11 ), sodium citrate, sodium tartrate, and sodium gluconate.

[0057] Hereinafter, embodiments of the present invention will be described in detail to facilitate easy implementation by those skilled in the art. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein. Furthermore, like reference numbers represent like elements throughout the specification.

[0058]

[0059] An artificial lightweight aggregate according to one embodiment of the present invention is based on fly ash, and by utilizing fly ash, it can replace conventional Portland cement, and can provide a carbon-reducing artificial lightweight aggregate based on a cement-free binder. Furthermore, by simultaneously utilizing a boron compound, it can provide an artificial lightweight aggregate for neutron shielding.

[0060]

[0061] A neutron shielding artificial lightweight aggregate according to one embodiment of the present invention comprises fly ash; calcium hydroxide (Ca(OH)2); sodium carbonate (Na2CO3), a boron compound, and an accelerator.

[0062] The above fly ash may be composed of silicon dioxide (SiO2) and aluminum oxide (Al2O3) as main materials, and more specifically, the fly ash may be composed of silicon dioxide (SiO2) and aluminum oxide (Al2O3) accounting for more than half of the total fly ash content.

[0063] In addition, the fly ash may include SiO2, Al2O3, CaO, and Fe2O3, and at this time, the fly ash may be distributed in the order of SiO2, Al2O3, CaO, and Fe2O3, and the content of the fly ash may be distributed in the order of SiO2 content, Al2O3 content, CaO content, and Fe2O3 content.

[0064] More specifically, the fly ash may be composed of SiO2, Al2O3, CaO, Fe2O3, MgO, TiO2, P2O5, K2O, Na2O, SO3, SrO, BaO, ZrO2, MnO, V2O5, ZnO, Cr2O3, CuO, NiO, Y2O3, and Ga2O3, and as an example, the fly ash may have a composition as shown in Table 1 below.

[0065]

[0066] The fly ash may be comprised of 55 to 69 wt%, the calcium hydroxide of 20 wt%, the sodium carbonate of 10 wt%, and the boron compound of 1 to 5 wt%, and the accelerator may be comprised of 0.6 wt% based on 100 wt% of the total of the fly ash, the calcium hydroxide, and the sodium carbonate.

[0067] The above boron compound may be boric acid (H3BO3) or borax (Na2B4O7).

[0068] The above promoter is sucrose (C 12 H 22 O 11 ), sodium citrate, sodium tartrate, and sodium gluconate.

[0069]

[0070] In addition, a method for manufacturing a neutron shielding artificial lightweight aggregate according to one embodiment of the present invention comprises the steps of preparing 100 parts by weight of a mixture of fly ash; calcium hydroxide (Ca(OH)2); sodium carbonate (Na2CO3), a boron compound, and an accelerator; a first pelletizing step of adding 90 parts by weight of the mixture and 27 parts by weight of water to a disk pelletizer; a second pelletizing step of additionally adding 10 parts by weight of the mixture to the disk pelletizer; and a third pelletizing step of additionally adding 3 parts by weight of water to the disk pelletizer.

[0071] The above fly ash may contain more than half of silicon dioxide (SiO2) and aluminum oxide (Al2O3).

[0072] The above fly ash contains SiO2, Al2O3, CaO and Fe2O3, and the fly ash may have a content distributed in the order of SiO2, Al2O3, CaO and Fe2O3.

[0073] The above fly ash may be composed of SiO2, Al2O3, CaO, Fe2O3, MgO, TiO2, P2O5, K2O, Na2O, SO3, SrO, BaO, ZrO2, MnO, V2O5, ZnO, Cr2O3, CuO, NiO, Y2O3, and Ga2O3.

[0074] The above mixture may include 55 to 69 wt% of the fly ash, 20 wt% of the calcium hydroxide, 10 wt% of the sodium carbonate, and 1 to 5 wt% of the boron compound, and the accelerator may be included in an amount of 0.6 parts by weight based on 100 parts by weight of the total of the fly ash, the calcium hydroxide, and the sodium carbonate.

[0075] The above boron compound may be boric acid (H3BO3) or borax (Na2B4O7).

[0076] The above promoter is sucrose (C 12 H 22 O 11 ), sodium citrate, sodium tartrate, and sodium gluconate.

[0077]

[0078] The above pelletizing step is a process of spherizing the mixture while rotating the disk pelletizer. The first pelletizing may be performed for 2 to 4 minutes (min), the second pelletizing may be performed for 5 to 8 minutes (min), and the third pelletizing may be performed for 5 to 8 minutes (min).

[0079]

[0080] Hereinafter, the present invention will be described in detail through examples. The following examples are intended only to facilitate understanding of the present invention and are not intended to limit the invention.

[0081]

[0082] Preparation Example 1. Preparation of fly ash

[0083] Fly ash (coal ash) having the composition shown in Table 1 below was prepared.

[0084] Fly AshOxideWeight %SiO248.94Al2O326.57CaO8.25Fe2O37.22MgO1.58TiO21.56P2O51.45K2O1.30Na2O1.23SO31.06SrO0. 26BaO0.26ZrO20.08MnO0.08V2O50.05ZnO0.02Cr2O30.02CuO0.02NiO0.02Y2O30.01Ga2O30.01Sum99.99

[0085]

[0086] Experimental Example 1. Particle Size Analysis

[0087] The particle size analysis results of the fly ash (raw fly ash) in the above Preparation Example 1 and the Portland cement having the composition shown in Table 2 below are shown in Figs. 1a and 1b. Fig. 1a shows the particle size analysis results of the fly ash in the above Preparation Example 1. Fig. 1b shows the particle size analysis results of the Portland cement having the composition shown in Table 2 below.

[0088] Portland cementOxideWeight %CaO65.40SiO217.15Al2O34.33MgO3.64SO33.55Fe2O33.53K2O1.19TiO20.34P2O50.19MnO0.18Na2O0.16ZnO0.11etc.0.23Total100

[0089]

[0090] Referring to FIG. 1a and FIG. 1b, referring to the density distribution and cumulative distribution, it can be confirmed that both fly ash (Preparation Example 1) and Portland cement have particle size distributions with similar trends.

[0091]

[0092] Example. Manufacturing of artificial lightweight aggregate

[0093] In the above preparation example 1 having the composition of Table 3 below, a premix containing fly ash, Ca(OH)2, Na2CO3, and a boron compound (H3BO3 or Na2B4O7) was added 0.6 parts by weight of sucrose (sugar, C) per 100 parts by weight of the premix. 12 H 22 O 11 ) to prepare 1000 g of the mixture, then, at room temperature (25°C) in a disk pelletizer (disk diameter: 400 mm, disk depth: 120 mm) at an inclination angle of 50° and a rotation speed of 46 rpm, 900 g of the mixture and 270 g of water are placed on the disk pelletizer, and then rotated for 3 minutes (1st pelletizing), then 100 g of the mixture is additionally placed, and then rotated for 5 minutes (2nd pelletizing), then 30 g of water is additionally placed, and then rotated for 5 minutes (3rd pelletizing), and then cured at 90°C for a total of 3 days.

[0094] Classification fly ash (preparation example 1) (wt%) Ca(OH)2 (wt%) Na2CO3 (wt%) H3BO3 (wt%) Na2B4O7 (wt%) C 12 H 22 O 11 (Weight) Example 176.315.38.4--0.6 Example 271.315.38.45-0.6 Example 371.315.38.4-50.6

[0095]

[0096] Comparative Example 1. Preparation of general crushed stone aggregate

[0097] As a comparative example, commercially available general crushed stone aggregate was prepared. The prepared general crushed stone aggregate complies with the ACI 211.1 standard, with a fineness modulus of 7.26, a surface dry specific gravity (SSD) of 2.68, a water absorption of 0.78%, and a unit weight of 1,601 kg / m. 3 , with a maximum coarse aggregate size of 19 mm.

[0098]

[0099] Experimental Example 2. Physical Properties

[0100] The aggregate crushing value according to BS 812 part 110 and the 10% crushing load (Ten percent fines value) according to BS 812 part 111 were measured for the general crushed stone aggregate of Comparative Example 1 and the artificial lightweight aggregates manufactured in Examples 1, 2, and 3, and the results are shown in Fig. 2. In Fig. 2, “Crushed-agg” is the general crushed stone aggregate of Comparative Example 1, “CNF-agg” is the artificial lightweight aggregate manufactured in Example 1, “CNF-HB-agg” is the artificial lightweight aggregate manufactured in Example 2, and “CNF-BX-agg” is the artificial lightweight aggregate manufactured in Example 3.

[0101] Referring to FIG. 2, it can be confirmed that the artificial lightweight aggregates manufactured in Examples 1, 2, and 3 have performances equivalent to those of general crushed stone aggregates.

[0102]

[0103] The Los Angeles abrasion resistance test according to ASTM C 131 was performed on the general crushed stone aggregate of Comparative Example 1 and the artificial lightweight aggregates manufactured in Examples 1, 23, and 3, and the results are shown in FIG. 3. In FIG. 3, “Crushed-agg” is the general crushed stone aggregate of Comparative Example, “CNF-agg” is the artificial lightweight aggregate manufactured in Example 1, “CNF-HB-agg” is the artificial lightweight aggregate manufactured in Example 2, and “CNF-BX-agg” is the artificial lightweight aggregate manufactured in Example 3.

[0104] Referring to FIG. 3, it can be confirmed that the artificial lightweight aggregates manufactured in Examples 1, 2, and 3 have an abrasion rate that satisfies the regulated limit of 40% or less.

[0105]

[0106] Various physical properties of the artificial lightweight aggregates manufactured in Examples 2 and 3 were measured and summarized in Table 4 below.

[0107] Classification Example 2 Example 3 Cut specific gravity 1.446 1.491 Table specific gravity 1.79 1.785 True specific gravity 2.206 2.112 Cut density (g / cm) 3 )1.4411.486 Loose bulk density (kg / m) 3 )671.705726.454Absorption rate(%)23.82919.75Porosity(%)53.54151.26Performance rate(%)46.45948.740

[0108]

[0109] Referring to Table 4, it can be confirmed that the dry density (Ministry of Land, Infrastructure and Transport Concrete Standard Specification) and loose bulk density (ASTM C 330) meet their respective standards.

[0110]

[0111] Experimental Example 3. XRD Analysis

[0112] XRD (X-ray Diffraction) analysis was performed on the general crushed stone aggregate of Comparative Example 1 and the artificial lightweight aggregates manufactured in Examples 1, 2, and 3, respectively, and the analysis results are shown in Fig. 4. In Fig. 4, “Crushed-agg” is the general crushed stone aggregate of Comparative Example 1, “CNF-agg” is the artificial lightweight aggregate manufactured in Example 1, “CNF-HB-agg” is the artificial lightweight aggregate manufactured in Example 2, and “CNF-BX-agg” is the artificial lightweight aggregate manufactured in Example 3.

[0113] Quantitative XRD analysis using Rietveld-RIR (reference-intensity-ratio) was performed to measure the crystallinity, and 10 wt% of Corundum (NIST SRM 676a) was included as an internal standard reference material, and then rescaled and normalized based on the absolute amount of Corundum.

[0114]

[0115] The results of XRD quantitative analysis for the general crushed stone aggregate of Comparative Example 1 and the artificial lightweight aggregate manufactured in Examples 2 and 3 are summarized in Table 5 below.

[0116] PhaseReference NumberContent (%)Comparative Example 1Example 2Example 3Quartz98-008-927726.711.711.9Andesine98-006-624045.9Biotite98-004-130410.1Clinochlore98-006-31935.2Mullite98-015-809818.118.1Calcite98-005-215127.430.1Corundum01-076-014412.142.839.9Total sum100100100Crystalline82.6423.3625.06Amorphous17.3676.6474.94

[0117] Referring to FIG. 4 and Table 5, it can be confirmed that the artificial lightweight aggregates manufactured in Examples 2 and 3 have an amorphous phase.

[0118]

[0119] Experimental Example 4. Analysis of heavy metal leaching (TCLP, Toxicity Characteristic Leaching Procedure) test

[0120] A TCLP test was performed on the artificial lightweight aggregates (samples) manufactured in Examples 2 and 3 above under the conditions of Table 6 below, and the results are summarized in Table 7 below.

[0121] Test conditions TCLP method Pretreatment of sample Grinding to 9.5 mm or less Shaking device Magnetic stirrer Shaking time 18 hours (hr) Solvent pH 4.93±0.05 Ratio of solvent: sample (w:w) 20:1 Solid-liquid separation 0.6 to 0.8 ㎛ membrane filter

[0122] Elemental standard value (ppm) Detected heavy metal concentration (ppm) Example 2 Example 3 Arsenic (As) 5.0 0.00 10.00 1 Cadmium (Cd) 1.0 ND ND Chromium (Cr) 5.0 ND ND ND mercury (Hg) 0.2 0.00 10.00 1 Lead (Pb) 5.0 ND ND

[0123]

[0124] Experimental Example 5. Boron Leaching Test Analysis

[0125] A boron leaching test was performed on the artificial lightweight aggregates (samples) manufactured in the above Examples 2 and 3, and the results are summarized in Table 7 below and illustrated in Fig. 5. In Fig. 5, “CNF-HB-agg” is the artificial lightweight aggregate manufactured in the above Example 2, and “CNF-BX-agg” is the artificial lightweight aggregate manufactured in the above Example 3.

[0126] The boron leaching test was conducted by preparing 1.00 kg of the artificial lightweight aggregate manufactured in the above Examples 2 and 3, setting the weight ratio of water and artificial lightweight aggregate at 25°C to 15 (water): 1 (artificial lightweight aggregate), and immersing it in water for 1 hour, 1 day, 1 week, and 1 month. After each immersion period, the amount of boron leaching was calculated through ICP-OES, and the results are shown in Fig. 5.

[0127] In Fig. 5, the amount of boron eluted after immersion for 1 month (Boron concentration at 1 month) and the leaching rate (Leachability) were calculated and summarized in Table 8 below.

[0128] Division Example 2Example 3Boron content in 1 kg of agg(mg)6694.158227.79Boron concentration at 1 month (mg / L)3.812.87Volume of leachate(L)15.0515.05Total leached boron amount (mg)57.3243.18Leachability(%)0.860.52

[0129]

[0130] Experimental Example 6. Compressive Strength Analysis of Artificial Lightweight Aggregate

[0131] The results of compressive strength analysis according to curing time (curing date) of 1 day (1d), 3 days (3d) (curing time in the example) and 7 days (7d) for the artificial lightweight aggregate manufactured in the above example are shown in Fig. 6. In Fig. 6, Example 1 is indicated as “CNF”, Example 2 is indicated as “CNF-BX 5%” and Example 3 is indicated as “CNF-BX 5%”.

[0132] Referring to Fig. 6, it can be confirmed that both the artificial aggregates of Examples 2 and 3, in which the amount of boric acid (H3BO3) and borax (Na2B4O7) added is 5 wt%, exhibit a strength of 30 MPa or more after 3 days of curing (curing time in the Examples), and it can be confirmed that both boric acid (H3BO3) and borax (Na2B4O7) can be mixed up to 15 wt%.

[0133]

[0134] Meanwhile, the results of the compressive strength analysis for Portland cement mixed with boron compounds according to the composition in Table 9 below at 1 day (1d), 3 days (3d), and 7 days (7d) based on the curing date are shown in Figure 7.

[0135] Classification Portland cement (wt%) H3BO3 (wt%) Na2B4O7 (wt%) PC100--PC-HB 5%955-PC-BX 5%95-5

[0136]

[0137] Referring to Figure 7, it can be confirmed that in the case of Portland cement, when boron is directly mixed, setting time is delayed, which inhibits setting and reduces compressive strength.

[0138]

[0139] Application examples. Concrete mix design

[0140] In Examples 1, 2, and 3, artificial lightweight aggregates were used to mix concrete according to the mixing ratios shown in Table 10 below. As a control, general concrete was mixed. The concrete was mixed to have a design strength of 40 MPa, a target slump of 100 ± 10 mm, and a trapped air content of 2 ± 1%. In particular, no admixtures such as water reducing agents or AE agents were used to ensure accurate neutron shielding experiments of the artificial aggregates.

[0141] Unit: kg / m 3Water Portland cement Coarse aggregate Fine aggregate Crushed-aggregate Example 1 Example 2 Example 3 Control group (general concrete) 183.92459.79 1000.19733.49 Application example 1 183.92459.79 581.55715.89 Application example 2 183.92459.79 515.71777.37 Application example 3 183.92459.79 539.37763.84

[0142] In the above Table 10, Portland cement is Type 1. In the above Table 9, both coarse aggregate (Comparative Example 1) and fine aggregate follow the ACI 211.1 standard, and the coarse aggregate of the comparative example (Crushed-agg) has a fineness modulus of 7.26, a surface dry internal saturated specific gravity (SSD) of 2.68, a water absorption of 0.78%, and a unit weight of 1,601 kg / m. 3 , the maximum coarse aggregate size is 19 mm. In Table 6 above, sand was used as fine aggregate, and the sand has a fineness modulus of 2.80, a surface dry internal saturated specific gravity (SSD) of 2.65, and a water absorption of 1.01%.

[0143]

[0144] Experimental Example 7. Concrete Compressive Strength Analysis

[0145] A compressive strength analysis was performed on the concrete of the control group and application examples mixed using the mixing ratios in Table 10 above, and the results of the compressive strength analysis are shown in Fig. 8. In Fig. 8, the compressive strength of the concrete of the control group was indicated as "CA-con", the compressive strength of the concrete of application example 1 was indicated as "CNF-con", the compressive strength of the concrete of application example 2 was indicated as "CNF-HB-con", and the compressive strength of the concrete of application example 2 was indicated as "CNF-BX-con". The compressive strength of the concrete was measured in accordance with ASTM C 39, and 100 x 200 mm cylinder specimens were manufactured and used for measuring the compressive strength after 7 and 28 days of curing.

[0146] Referring to FIG. 8, it can be confirmed that the concrete of application examples 1 to 3 using the artificial lightweight aggregate manufactured in Examples 1, 2, and 3 as coarse aggregate satisfies both ACI 213 (17 MPa as a standard for 28-day compressive strength of concrete) and KS F 2527 (27 MPa as a standard for compressive strength of concrete).

[0147]

[0148] Experimental Example 8. Analysis of Neutron Shielding Experiment Results

[0149] The concrete manufactured in the above application example was made into a rectangular specimen measuring 150 x 150 x 50 mm, and the neutron shielding performance was measured after 28 days of curing. The neutron shielding performance 241 Am-Be (neutron energy emission rate: 1.227 x 10 7 s -1 ) was used as a neutron source, and the source was placed inside a high-purity graphite block to moderate fast neutrons into thermal neutrons before conducting the experiment. An SP9 3He proportional counter was used to detect thermal neutrons, and the thermal neutron shielding ratio was calculated using the following equation 1.

[0150] [Formula 1]

[0151]

[0152] In the above equation 1, S th Thermal neutron counting rate passing through the specimen(s -1 ) and R air Thermal neutron counting rate at air without the specimen(s -1 )am.

[0153] The results of the neutron shielding performance analysis performed in this experimental example are summarized in Table 11 below. In Table 11, U R is the relative uncertainty (%).

[0154] The results of the neutron shielding performance analysis performed in this experimental example are summarized in Table 11 below. In Table 11, U R is the relative uncertainty (%).

[0155] LabelThermal Neutron Counting Rate, s -1 Shielding Efficiency, % (U R )Air78.59-Control15.7779.93 (0.24)Application example 22.6896.59 (0.04)Application example 30.5499.31 (0.02)

[0156] Referring to Table 11, significantly high neutron shielding rates of 99.31% and 96.59% were confirmed, confirming the potential of a cement-free, amorphous, artificial lightweight aggregate with neutron shielding performance. This suggests that this artificial lightweight aggregate can be used not only in nuclear facilities but also in all concrete structures requiring neutron shielding performance.

[0157]

[0158] Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims also fall within the scope of the present invention.

Claims

1. Contains fly ash; calcium hydroxide (Ca(OH)2); sodium carbonate (Na2CO3), boron compounds and accelerators. The above fly ash is composed of more than half of silicon dioxide (SiO2) and aluminum oxide (Al2O3). Neutron shielding artificial lightweight aggregate.

2. In paragraph 1, The above fly ash contains SiO2, Al2O3, CaO and Fe2O3. Neutron shielding artificial lightweight aggregate.

3. In paragraph 2, The above fly ash is distributed in the order of SiO2, Al2O3, CaO and Fe2O3. Neutron shielding artificial lightweight aggregate.

4. In paragraph 1, The above fly ash is composed of SiO2, Al2O3, CaO, Fe2O3, MgO, TiO2, P2O5, K2O, Na2O, SO3, SrO, BaO, ZrO2, MnO, V2O5, ZnO, Cr2O3, CuO, NiO, Y2O3 and Ga2O3. Neutron shielding artificial lightweight aggregate.

5. In paragraph 1, Contains 55 to 69 wt% of the fly ash, 20 wt% of the calcium hydroxide, 10 wt% of the sodium carbonate, and 1 to 5 wt% of the boron compound, The above accelerator is included in an amount of 0.6 parts by weight relative to a total of 100 parts by weight of the fly ash, the calcium hydroxide, and the sodium carbonate. Neutron shielding artificial lightweight aggregate.

6. In paragraph 1, The above boron compound is boric acid (H3BO3) or borax (Na2B4O7). Neutron shielding artificial lightweight aggregate.

7. In paragraph 1, The above promoter is sucrose (C 12 H 22 O 11 ), sodium citrate, sodium tartrate and sodium gluconate, one or more substances selected from the group consisting of Neutron shielding artificial lightweight aggregate.

8. A step of preparing 100 parts by weight of a mixture of fly ash, calcium hydroxide (Ca(OH)2), sodium carbonate (Na2CO3), boron compound, and accelerator; A first pelletizing step of putting 90 parts by weight of the above mixture and 27 parts by weight of water onto a disk pelletizer; A second pelletizing step of adding 10 parts by weight of the mixture onto the disk pelletizer; and It includes a third pelletizing step of adding 3 parts by weight of water to the above disk pelletizer, The above fly ash is composed of more than half of silicon dioxide (SiO2) and aluminum oxide (Al2O3). Method for manufacturing neutron shielding artificial lightweight aggregate.

9. In paragraph 8, The above fly ash contains SiO2, Al2O3, CaO and Fe2O3. Method for manufacturing neutron shielding artificial lightweight aggregate.

10. In paragraph 9, The above fly ash is distributed in the order of SiO2, Al2O3, CaO and Fe2O3. Method for manufacturing neutron shielding artificial lightweight aggregate.

11. In paragraph 8, The above fly ash is composed of SiO2, Al2O3, CaO, Fe2O3, MgO, TiO2, P2O5, K2O, Na2O, SO3, SrO, BaO, ZrO2, MnO, V2O5, ZnO, Cr2O3, CuO, NiO, Y2O3 and Ga2O3. Method for manufacturing neutron shielding artificial lightweight aggregate.

12. In paragraph 8, The above mixture. Contains 55 to 69 wt% of the fly ash, 20 wt% of the calcium hydroxide, 10 wt% of the sodium carbonate, and 1 to 5 wt% of the boron compound, The above accelerator is included in an amount of 0.6 parts by weight relative to a total of 100 parts by weight of the fly ash, the calcium hydroxide, and the sodium carbonate. Method for manufacturing neutron shielding artificial lightweight aggregate.

13. In paragraph 8, The above boron compound is boric acid (H3BO3) or borax (Na2B4O7). Method for manufacturing neutron shielding artificial lightweight aggregate.

14. In paragraph 8, The above promoter is sucrose (C 12 H 22 O 11 ), sodium citrate, sodium tartrate and sodium gluconate, one or more substances selected from the group consisting of Method for manufacturing neutron shielding artificial lightweight aggregate.

Images