Functional aggregate for radiation-proof ultra-high performance concrete and preparation method thereof

Abstract

The application discloses a kind of functional aggregate for radiation-proof ultra-high performance concrete and a preparation method thereof, and belongs to the field of building materials.The functional aggregate includes core and shell wrapped on the surface of the core;By weight parts, the core includes the following components: electroplating sludge 35-40 parts, barite powder 8-15 parts, sodium borocalcite 25-35 parts, red mud 15-25 parts, thickening agent 3-7 parts;By weight parts, the shell includes the following components: modified waste paper sludge 50-60 parts, spodumene 3-5 parts, glass powder 5-10 parts, vermiculite 5-10 parts, high-iron steel slag 30-40 parts.The functional aggregate of the application has significant effect on resisting multiple radiation, high roundness and strength, and also has internal curing function, and can be widely applied to military protection and medical buildings.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a functional aggregate for radiation-resistant ultra-high performance concrete and its preparation method. Background Technology

[0002] Radiation-shielding concrete, as the main structural material in nuclear engineering construction, must both shield harmful radiation and ensure structural safety. Therefore, it must possess excellent radiation shielding and mechanical properties simultaneously. However, the current design strength of radiation-shielding concrete is generally not high, with strength grades typically not exceeding C60. This makes it difficult to withstand high-intensity dynamic loads caused by explosive impacts or major geological disasters, posing a potential threat to the structural safety of nuclear facilities.

[0003] Ultra-high performance concrete (UHPC), a cement-based concrete material with superior mechanical properties, high toughness, ultra-high durability, and excellent casting and molding performance, is attracting increasing attention. Aggregates, accounting for approximately 50% of the raw materials of UHPC, are a key factor affecting its mechanical properties and radiation protection capabilities. However, due to the lack of specialized aggregates for radiation-proof UHPC, current practices, drawing on the concepts of traditional radiation-proof concrete, still utilize aggregates such as barite, hematite, and serpentine. However, due to the significant differences in composition and structure between UHPC and ordinary concrete, directly copying traditional methods will face the following problems: (1) Commonly used natural radiation-shielding aggregates such as barite sand are brittle and easily pulverized. When preparing UHPC, their strength is 20%-30% lower than that of concrete prepared using the same silica sand; (2) UHPC has a low water-cement ratio and low crystal water content, resulting in low neutron radiation absorption capacity; (3) UHPC requires less water and has high autogenous shrinkage. It is often internally cured with superabsorbent polymer (SAP). However, after SAP releases water and shrinks, it will leave pores in the concrete, reducing the radiation protection performance of UHPC. Therefore, there is an urgent need to prepare functional aggregates for UHPC that are resistant to multiple types of radiation, have high strength, and have internal curing effects. Summary of the Invention

[0004] In view of this, the present invention aims to provide a functional aggregate for radiation-resistant ultra-high performance concrete. This functional aggregate has significant radiation protection effects, high roundness and strength, and also has internal curing function. It can be widely used in military protection and medical buildings, effectively solving the problem that the existing radiation-resistant aggregates have low strength and cannot meet the requirements of radiation-resistant UHPC products.

[0005] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0006] A functional aggregate for radiation-resistant ultra-high performance concrete includes a core and an outer shell covering the surface of the core. By weight, the core comprises the following components: 35-40 parts electroplating sludge, 8-15 parts barite powder, 25-35 parts sodium borate, 15-25 parts red mud, and 3-7 parts thickener. By weight, the outer shell comprises the following components: 50-60 parts modified waste paper sludge, 3-5 parts spodumene, 5-10 parts glass powder, 5-10 parts vermiculite, and 30-40 parts high-speed rail steel slag.

[0007] Optionally, the electroplating sludge contains ≥20% Cr2O3 and ≥10% ZnO by mass.

[0008] Optionally, the mass content of B2O3 in the sodium borate is ≥45%.

[0009] Optionally, the red mud contains ≥10% SiO2 and ≥30% Al2O3 by mass.

[0010] Optionally, the thickener is composed of water glass and sodium aluminate in a mass ratio of 1:1 to 1:3.

[0011] Optionally, the modified waste paper sludge is prepared by mixing waste paper sludge and sodium hydroxide at a mass ratio of 17:3 to 19:1, and mixing for 2 to 3 hours under the conditions of a water-to-material ratio of 1:1 to 2:3 and a ball-to-material ratio of 1:1 to 1:3.

[0012] Optionally, the particle size of the spodumene, the glass powder, and the vermiculite is all less than 5% on a 200-mesh sieve.

[0013] Optionally, the high-speed rail steel slag contains ≥30% Fe2O3 by mass and ≥40% SiO2+Al2O3 by mass.

[0014] A second objective of this invention is to provide a method for preparing the above-mentioned functional aggregate for radiation-resistant ultra-high performance concrete, the method comprising the following steps:

[0015] 1) The spodumene, glass powder, vermiculite and high-speed iron slag are added to the modified waste paper sludge and mixed for 1-2 hours to obtain a mixed slurry. The mixed slurry is freeze-dried under a vacuum of 2-5 kPa to obtain the shell material.

[0016] 2) The electroplating sludge, the barite powder, the sodium borate, the red mud and the thickener are mixed and granulated at a rotation speed of 30-40 r / min to obtain a core blank;

[0017] 3) Wrap the outer shell material around the surface of the core blank to obtain a functional aggregate sphere blank;

[0018] 4) Dry the functional aggregate spherical blanks at 60°C for 1-2 hours, and then sinter them at 950-1100°C for 20-30 minutes to obtain functional aggregates for radiation-resistant ultra-high performance concrete.

[0019] Optionally, the diameter of the core blank in step 2) is 3-8 mm and the moisture content is 15-30%; the diameter of the functional aggregate sphere blank in step 3) is 5-10 mm and the moisture content is 15-30%.

[0020] Compared with existing technologies, the functional aggregate for radiation-resistant ultra-high performance concrete described in this invention has the following advantages:

[0021] 1. This invention provides a functional aggregate for ultra-high performance radiation-resistant concrete, offering excellent protection against gamma rays, X-rays, and neutron radiation while maintaining high environmental safety. The core material primarily consists of electroplating sludge containing a large amount of heavy metals, barite powder, and sodium borate containing a large amount of light elements, thus providing excellent shielding against gamma rays, X-rays, and neutron radiation. The outer shell contains lithium and high-iron steel slag containing a large amount of iron, which can shield against gamma and X-ray radiation and slow down and absorb fast neutrons, further enhancing its radiation protection function. Furthermore, during the preparation process, radiation-resistant elements such as Cr, Zn, and B, which are significantly harmful to humans and the environment, react with silicon dioxide and alumina to form stable crystals and a glassy phase. The outer shell then acts as another layer of encapsulation and sealing, resulting in high safety and stability.

[0022] 2. The aggregate provided by this invention has high strength and a simple process. Compared with the two-stage pelletizing of traditional core-shell aggregates, the functional aggregate of this invention only requires one-stage pelletizing. During the sintering process, red mud is used to adjust the silicon-aluminum composition in the core raw materials, giving the core higher strength. Water glass and sodium aluminate are used as thickeners, which on the one hand helps to ensure uniform mixing of raw materials containing heavy and light elements and maintain good sphericity, and on the other hand, they play an activation role, which is beneficial to further improve the core strength. The shell uses modified waste paper sludge and high-iron steel slag, which have high activity and complete reaction, providing good strength. The modified waste paper sludge contains a large amount of paper fiber, which plays a good reinforcing role. In addition, considering that the synergistic deformation of the core and shell structural materials and the sintering regime have a significant impact on their final strength, spodumene and glass powder are used to further activate them, making the optimal sintering temperature of the core and shell close and further improving the shell strength.

[0023] 3. The aggregate provided by this invention exhibits excellent internal curing effect, achieving a shell porosity of 55-75%. Traditional porous material preparation processes are prone to collapse during drying. However, the shell material prepared by this invention utilizes modified waste paper sludge and vermiculite, resulting in high porosity and a rich pore structure. During liquid-phase grinding with other raw materials, fine particles can fill these pores. During drying, the fibers and vermiculite in the waste paper sludge provide excellent skeletal support and reinforcement. During sintering, the fibers are burned off, while the vermiculite expands, leaving behind numerous pores. At this point, the fine particles within the pores can fully react and bond together, improving strength. Furthermore, the vermiculite after high-temperature sintering has excellent water absorption and release properties, further ensuring the internal curing effect of the aggregate. Detailed Implementation

[0024] To enable those skilled in the art to better understand the technical solutions and effects of the present invention, several embodiments will be provided below. Obviously, the following description is only an embodiment and does not limit the scope of protection of the present invention.

[0025] The technical specifications of the raw materials used in the following examples are as follows:

[0026] The electroplating sludge originated from industrial sludge containing Cr and Zn from relevant enterprises in Wuhan, Hubei Province. The mass content of Cr2O3 was 23%, and the mass content of ZnO was 17%. The mass content of B2O3 in sodium borate was 48%. The mass content of SiO2 in red mud was 32%, and the mass content of Al2O3 was 38%. The modulus of water glass was 1.4, and the sodium aluminate was industrial grade sodium aluminate. The waste paper sludge originated from the primary sedimentation tank of a paper mill in Wuhan, Hubei Province, with an organic matter content of 62%. The sodium hydroxide was a commercially available material. The residues of spodumene, glass powder, and vermiculite after passing through a 200-mesh sieve were 1.2%, 0.8%, and 2.3%, respectively. The mass content of Fe2O3 in high-speed iron steel slag was 42%, and the mass content of SiO2+Al2O3 was 47%.

[0027] Example 1

[0028] A functional aggregate for radiation-resistant ultra-high performance concrete is prepared by the following method:

[0029] 1) By weight, 3 parts spodumene, 10 parts glass powder, 5 parts vermiculite and 30 parts high-speed iron slag are added to 60 parts modified waste paper sludge and mixed for 1 hour to obtain a mixed slurry. The mixed slurry is freeze-dried under vacuum conditions of 2 kPa to obtain the shell material. The modified waste paper sludge is prepared by mixing waste paper sludge and sodium hydroxide at a mass ratio of 17:3 and mixing for 2 hours under the conditions of water-to-material ratio of 1:1 and ball-to-material ratio of 1:1.

[0030] 2) By weight, 35 parts of electroplating sludge, 8 parts of barite powder, 25 parts of sodium borate, 25 parts of red mud and 7 parts of thickener are mixed and granulated at a speed of 30 r / min to obtain a core blank with a diameter of 8 mm and a moisture content of 30%. The thickener is composed of water glass and sodium aluminate in a mass ratio of 1:1.

[0031] 3) Using the same granulation conditions as in step 2), wrap the outer shell material obtained in step 1) around the surface of the core blank obtained in step 2) to obtain a functional aggregate sphere blank with a diameter of 10 mm and a moisture content of 30%.

[0032] 4) Dry the functional aggregate spherical blanks obtained in step 3) at 60°C for 1 hour, and then sinter them at 1050°C for 40 minutes to obtain functional aggregates for radiation-resistant ultra-high performance concrete.

[0033] The performance of the functional aggregate for radiation-shielding ultra-high performance concrete prepared in this embodiment was tested. The tests showed that the compressive strength of the functional aggregate for radiation-shielding ultra-high performance concrete prepared in this embodiment was 16.7 MPa, the water absorption rate was 27%, and the gamma-ray shielding coefficient μ was 0.21 cm⁻¹. -1 The neutron radiation shielding coefficient μ is 0.20 cm. -1 The porosity of the outer shell is 50%.

[0034] Example 2

[0035] A functional aggregate for radiation-resistant ultra-high performance concrete is prepared by the following method:

[0036] 1) By weight, 5 parts spodumene, 5 parts glass powder, 10 parts vermiculite and 40 parts high-speed iron slag are added to 50 parts modified waste paper sludge and mixed for 2 hours to obtain a mixed slurry. The mixed slurry is freeze-dried under a vacuum of 5 kPa to obtain the shell material. The modified waste paper sludge is prepared by mixing waste paper sludge and sodium hydroxide at a mass ratio of 19:1 and mixing for 3 hours under the conditions of a water-to-material ratio of 2:3 and a ball-to-material ratio of 1:3.

[0037] 2) By weight, 40 parts of electroplating sludge, 15 parts of barite powder, 35 parts of sodium borate, 15 parts of red mud and 3 parts of thickener are mixed and granulated at a speed of 40 r / min to obtain a core blank with a diameter of 3 mm and a moisture content of 15%. The thickener is composed of water glass and sodium aluminate in a mass ratio of 1:3.

[0038] 3) Using the same granulation conditions as in step 2), wrap the outer shell material obtained in step 1) around the surface of the core blank obtained in step 2) to obtain a functional aggregate sphere blank with a diameter of 5 mm and a moisture content of 15%.

[0039] 4) Dry the functional aggregate spherical blanks obtained in step 3) at 60°C for 2 hours, and then sinter them at 950°C for 40 minutes to obtain functional aggregates for radiation-resistant ultra-high performance concrete.

[0040] The performance of the functional aggregate for radiation-shielding ultra-high performance concrete prepared in this embodiment was tested. The tests showed that the compressive strength of the functional aggregate for radiation-shielding ultra-high performance concrete prepared in this embodiment was 10.6 MPa, the water absorption rate was 32%, and the gamma-ray shielding coefficient μ was 0.27 cm⁻¹. -1 The neutron beam shielding coefficient μ is 0.25 cm. -1 The porosity of the outer shell is 75%.

[0041] Example 3

[0042] A functional aggregate for radiation-resistant ultra-high performance concrete is prepared by the following method:

[0043] 1) By weight, 4 parts spodumene, 8 parts glass powder, 8 parts vermiculite and 35 parts high-speed iron slag were added to 55 parts modified waste paper sludge and mixed for 2.5 hours to obtain a mixed slurry. The mixed slurry was freeze-dried under vacuum conditions of 4 kPa to obtain the shell material. The modified waste paper sludge was prepared by mixing waste paper sludge and sodium hydroxide at a mass ratio of 10:1 and mixing for 2 hours under the conditions of water-to-material ratio of 1:1.3 and ball-to-material ratio of 1:2.

[0044] 2) By weight, 38 parts of electroplating sludge, 12 parts of barite powder, 30 parts of sodium borate, 20 parts of red mud and 5 parts of thickener were mixed and granulated at a speed of 35 r / min to obtain a core blank with a diameter of 5 mm and a moisture content of 20%. The thickener was composed of water glass and sodium aluminate in a mass ratio of 1:3.

[0045] 3) Using the same granulation conditions as in step 2), wrap the outer shell material obtained in step 1) around the surface of the core blank obtained in step 2) to obtain a functional aggregate sphere blank with a diameter of 8 mm and a moisture content of 20%.

[0046] 4) Dry the functional aggregate spherical blanks obtained in step 3) at 60°C for 1.5 h, and then sinter them at 1000°C for 30 min to obtain functional aggregates for radiation-resistant ultra-high performance concrete.

[0047] The performance of the functional aggregate for radiation-shielding ultra-high performance concrete prepared in this embodiment was tested. The tests showed that the compressive strength of the functional aggregate for radiation-shielding ultra-high performance concrete prepared in this embodiment was 12.1 MPa, the water absorption rate was 29%, and the gamma-ray shielding coefficient μ was 0.23 cm⁻¹. -1 The neutron radiation shielding coefficient μ is 0.22 cm. -1 The porosity of the outer shell is 62%.

[0048] Example 4

[0049] A functional aggregate for radiation-resistant ultra-high performance concrete is prepared by the following method:

[0050] 1) By weight, 4 parts spodumene, 8 parts glass powder, 8 parts vermiculite and 35 parts high-speed iron slag were added to 55 parts modified waste paper sludge and mixed for 2.5 hours to obtain a mixed slurry. The mixed slurry was freeze-dried under vacuum conditions of 4 kPa to obtain the shell material. The modified waste paper sludge was prepared by mixing waste paper sludge and sodium hydroxide at a mass ratio of 10:1 and mixing for 2 hours under the conditions of water-to-material ratio of 1:1.3 and ball-to-material ratio of 1:2.

[0051] 2) By weight, 38 parts of electroplating sludge, 12 parts of barite powder, 35 parts of sodium borate, 20 parts of red mud and 5 parts of thickener are mixed and granulated at a speed of 35 r / min to obtain a core blank with a diameter of 5 mm and a water content of 25%. The thickener is composed of water glass and sodium aluminate in a mass ratio of 1:3.

[0052] 3) Using the same granulation conditions as in step 2), wrap the outer shell material obtained in step 1) around the surface of the core blank obtained in step 2) to obtain a functional aggregate sphere blank with a diameter of 8 mm and a moisture content of 25%.

[0053] 4) Dry the functional aggregate spherical blanks obtained in step 3) at 60°C for 1.5 h, and then sinter them at 1000°C for 30 min to obtain functional aggregates for radiation-resistant ultra-high performance concrete.

[0054] The performance of the functional aggregate for radiation-shielding ultra-high performance concrete prepared in this embodiment was tested. The tests showed that the compressive strength of the functional aggregate for radiation-shielding ultra-high performance concrete prepared in this embodiment was 10.9 MPa, the water absorption rate was 30%, and the gamma-ray shielding coefficient μ was 0.23 cm⁻¹. -1 The neutron radiation shielding coefficient μ is 0.23 cm. -1 The porosity of the outer shell is 67%.

[0055] Example 5

[0056] A functional aggregate for radiation-resistant ultra-high performance concrete is prepared by the following method:

[0057] 1) By weight, 4 parts of spodumene, 8 parts of glass powder, 8 parts of vermiculite and 40 parts of high-speed iron slag are added to 55 parts of modified waste paper sludge and mixed for 2.5 hours to obtain a mixed slurry. The mixed slurry is freeze-dried under a vacuum of 4 kPa to obtain the shell material. The modified waste paper sludge is prepared by mixing waste paper sludge and sodium hydroxide at a mass ratio of 10:1 and mixing for 2 hours under the conditions of a water-to-material ratio of 1:1.3 and a ball-to-material ratio of 1:2.

[0058] 2) By weight, 38 parts of electroplating sludge, 12 parts of barite powder, 30 parts of sodium borate, 20 parts of red mud and 5 parts of thickener are mixed and granulated at a speed of 35 r / min to obtain a core blank with a diameter of 5 mm and a moisture content of 25%. The thickener is composed of water glass and sodium aluminate in a mass ratio of 1:3.

[0059] 3) Using the same granulation conditions as in step 2), wrap the outer shell material obtained in step 1) around the surface of the core blank obtained in step 2) to obtain a functional aggregate sphere blank with a diameter of 8 mm and a moisture content of 25%.

[0060] 4) Dry the functional aggregate spherical blanks obtained in step 3) at 60°C for 1.5 h, and then sinter them at 1000°C for 30 min to obtain functional aggregates for radiation-resistant ultra-high performance concrete.

[0061] The performance of the functional aggregate for radiation-shielding ultra-high performance concrete prepared in this embodiment was tested. The tests showed that the compressive strength of the functional aggregate for radiation-shielding ultra-high performance concrete prepared in this embodiment was 12.8 MPa, the water absorption rate was 27%, and the gamma-ray shielding coefficient μ was 0.25 cm⁻¹. -1 The neutron radiation shielding coefficient μ is 0.24 cm. -1 The porosity of the outer shell is 56%.

[0062] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A functional aggregate for radiation-resistant ultra-high performance concrete, characterized in that, The system comprises a core and a shell encasing the surface of the core. By weight, the core comprises the following components: 35-40 parts electroplating sludge, 8-15 parts barite powder, 25-35 parts sodium borate, 15-25 parts red mud, and 3-7 parts thickener. By weight, the shell comprises the following components: 50-60 parts modified waste paper sludge, 3-5 parts spodumene, 5-10 parts glass powder, 5-10 parts vermiculite, and 30-40 parts high-speed iron slag. The thickener is composed of water glass and sodium aluminate in a mass ratio of 1:1 to 1:

3. The modified waste paper sludge is prepared by mixing waste paper sludge and sodium hydroxide at a mass ratio of 17:3 to 19:1, and mixing for 2 to 3 hours under the conditions of a water-to-material ratio of 1:1 to 2:3 and a ball-to-material ratio of 1:1 to 1:

3. The functional aggregate for radiation-resistant ultra-high performance concrete is prepared by the following method: 1) The spodumene, glass powder, vermiculite and high-speed iron slag are added to the modified waste paper sludge and mixed for 1-2 hours to obtain a mixed slurry. The mixed slurry is freeze-dried under vacuum conditions of 2-5 kPa to obtain the shell material. 2) The electroplating sludge, the barite powder, the sodium borate, the red mud and the thickener are mixed and granulated at a rotation speed of 30~40 r / min to obtain a core blank; 3) Wrap the outer shell material around the surface of the core blank to obtain a functional aggregate sphere blank; 4) Dry the functional aggregate spherical blanks at 60°C for 1-2 hours, and then sinter them at 950-1100°C for 20-30 minutes to obtain functional aggregates for radiation-resistant ultra-high performance concrete.

2. The functional aggregate for radiation-resistant ultra-high performance concrete according to claim 1, characterized in that, The electroplating sludge contains Cr2O3 with a mass content of ≥20% and ZnO with a mass content of ≥10%.

3. The functional aggregate for radiation-resistant ultra-high performance concrete according to claim 1, characterized in that, The sodium borate contains ≥45% B2O3 by mass.

4. The functional aggregate for radiation-resistant ultra-high performance concrete according to claim 1, characterized in that, The red mud contains ≥10% SiO2 and ≥30% Al2O3 by mass.

5. The functional aggregate for radiation-resistant ultra-high performance concrete according to claim 1, characterized in that, The spodumene, the glass powder, and the vermiculite all have a particle size of less than 5% on a 200-mesh sieve.

6. The functional aggregate for radiation-resistant ultra-high performance concrete according to claim 1, characterized in that, The high-speed rail steel slag contains ≥30% Fe2O3 and ≥40% SiO2+Al2O3 by mass.

7. A method for preparing the functional aggregate for radiation-resistant ultra-high performance concrete according to any one of claims 1 to 6, characterized in that, Includes the following steps: 1) The spodumene, glass powder, vermiculite and high-speed iron slag are added to the modified waste paper sludge and mixed for 1-2 hours to obtain a mixed slurry. The mixed slurry is freeze-dried under vacuum conditions of 2-5 kPa to obtain the shell material. 2) The electroplating sludge, the barite powder, the sodium borate, the red mud and the thickener are mixed and granulated at a rotation speed of 30~40 r / min to obtain a core blank; 3) Wrap the outer shell material around the surface of the core blank to obtain a functional aggregate sphere blank; 4) Dry the functional aggregate spherical blanks at 60°C for 1-2 hours, and then sinter them at 950-1100°C for 20-30 minutes to obtain functional aggregates for radiation-resistant ultra-high performance concrete.

8. The method for preparing functional aggregates for radiation-resistant ultra-high performance concrete according to claim 7, characterized in that, The diameter of the core blank in step 2) is 3-8 mm and the moisture content is 15-30%; the diameter of the functional aggregate sphere blank in step 3) is 5-10 mm and the moisture content is 15-30%.