A low-carbon concrete with a large amount of industrial solid waste and a preparation method thereof

Abstract

This invention relates to the field of concrete, and more particularly to a low-carbon concrete with a high dosage of industrial solid waste and its preparation method. By weight, its components include: cement: 170 parts; fly ash: 170 parts; fine aggregate: 600-800 parts; coarse aggregate: 1000 parts; water: 132 parts; polycarboxylate superplasticizer: 1 part; and modified material MIL53(Al-Fe)@SiO2: 1-5 parts. The invention prepares the MIL53(Al-Fe)@SiO2 modified material through in-situ conversion of fly ash and waste aluminum foil, and applies it to a 1:1 cement-fly ash high-dosage solid waste system. This method maintains high strength above 50 MPa and stable mechanical properties while significantly enhancing the density of the concrete, reducing chloride ion permeability from 0.34% to 0.18%, a reduction of 47.1%. This invention not only realizes the high-value utilization and low-carbon emission reduction of industrial solid waste, but also significantly improves the durability of concrete in harsh environments, and has significant environmental protection and engineering application value.

Description

Technical Field

[0001] This invention relates to the field of concrete, and more particularly to a low-carbon concrete with a large amount of industrial solid waste and its preparation method. Background Technology

[0002] Concrete, as the world's most consumed building material, emits a significant amount of carbon dioxide during the production of its core binder, cement. To reduce its carbon footprint, using industrial solid waste to partially replace cement in the production of concrete with high solid waste content has become a key path to achieving sustainable development in the construction industry.

[0003] Fly ash, as a major solid waste emitted by coal-fired power plants, possesses excellent pozzolanic activity and morphological effects. Its application in concrete not only consumes industrial waste and reduces environmental pollution but also effectively lowers concrete production costs. However, in the practical application of high-volume fly ash concrete, several technical bottlenecks still urgently need to be addressed:

[0004] First, there is a contradiction between mechanical properties and admixture dosage. Although fly ash can improve the later-stage strength of concrete, a large admixture often leads to slow early-stage strength improvement. Furthermore, as the replacement ratio increases, the compactness of the concrete may be affected, making it difficult to meet the requirements of high-performance engineering in terms of elastic modulus and compressive strength.

[0005] Secondly, there is the issue of durability, particularly resistance to chloride ion corrosion. In coastal buildings, cross-sea bridges, or saline soil areas, chloride ion penetration is a major cause of steel reinforcement corrosion, leading to the destruction of concrete structures. In high-volume fly ash systems, the porosity of the microstructure and the quality of the interfacial transition zone directly determine the anti-permeability performance during long-term service. While existing chemical admixtures can improve performance to some extent, they often have limited functionality and cannot simultaneously achieve both efficient utilization of solid waste resources and a fundamental improvement in durability.

[0006] Furthermore, the added value of solid waste utilization is low. Current resource utilization methods mostly remain at the level of physical filling or simple chemical activation, lacking means for deep chemical transformation and functional modification of industrial solid waste.

[0007] In recent years, metal-organic frameworks (MOFs) have shown great potential in adsorption, catalysis, and material modification due to their ultra-high specific surface area, tunable pore structure, and good chemical stability. However, traditional MOF materials are expensive to synthesize, and their direct addition to concrete can easily lead to uneven dispersion or failure under alkaline conditions.

[0008] Therefore, how to utilize low-cost in-situ conversion of industrial solid waste to prepare high-performance modifying and reinforcing agents, and significantly improve the mechanical properties and resistance to chloride ion erosion of concrete while ensuring high solid waste content, and develop a truly high-strength, long-life, low-carbon emission, high-volume industrial solid waste low-carbon concrete, is a key issue that urgently needs to be addressed in the field of civil engineering materials. Summary of the Invention

[0009] To address the technical problems existing in the prior art, this invention provides a low-carbon concrete with a large amount of industrial solid waste and its preparation method.

[0010] This invention is achieved through the following technical solution:

[0011] A low-carbon concrete with high dosage of industrial solid waste, by weight, comprises: cement: 170 parts; fly ash: 170 parts; fine aggregate: 600-800 parts; coarse aggregate: 1000 parts; water: 132 parts; polycarboxylate superplasticizer: 1 part; and modified material MIL53(Al-Fe)@SiO2: 1-5 parts.

[0012] Furthermore, the main components and their mass percentages of the fly ash are: CaO 35.5%, SiO2 38.9%, Al2O3 13.4%, Fe2O3 4.6%, and MgO 2.8%.

[0013] Furthermore, the coarse aggregate is crushed stone with a particle size distribution between 10 and 20 mm; the fine aggregate is river sand with a particle size distribution between 2 and 4.5 mm.

[0014] Furthermore, the preferred amount of the modified material MIL53(Al-Fe)@SiO2 is 3 to 5 parts.

[0015] This invention also provides a method for preparing low-carbon concrete with a large amount of industrial solid waste, comprising the following steps:

[0016] S1. Weigh out cement, fly ash, fine aggregate, coarse aggregate and modified material MIL53(Al-Fe)@SiO2 according to the proportion, and put them into the mixer for mixing;

[0017] S2. Mix the polycarboxylate superplasticizer with water until homogeneous to obtain a mixing solution;

[0018] S3. Add the mixing liquid obtained in step S2 to the dry material in step S1, and continue stirring until uniform to obtain the high-volume industrial solid waste low-carbon concrete.

[0019] Furthermore, the preparation method of MIL53(Al-Fe)@SiO2 includes the following steps:

[0020] S21. After washing, fly ash and waste aluminum foil are dried at 110°C;

[0021] S22. Mix the dried fly ash, aluminum foil and ferric chloride, wherein the weight ratio of fly ash to aluminum foil is 1:0.6, and the weight ratio of the three after adding ferric chloride is 0.625:0.375:5;

[0022] S23. Add a 35% HNO3 solution to the above mixture and boil at 130°C for 45 minutes to convert aluminum oxide and ferric chloride into aluminum nitrate and ferric nitrate in situ.

[0023] S24. After boiling, dry the mixture, add terephthalic acid at a weight ratio of 1:1, and then disperse it in a mixed solvent of DMF and distilled water, wherein the volume ratio of DMF to distilled water is 1:2.

[0024] S25. After stirring continuously at 40°C for 1 hour, transfer to a stainless steel high-pressure reactor and maintain at 150°C for 72 hours;

[0025] S26. After the reaction vessel has cooled to room temperature, wash it repeatedly with ultrapure water and ethanol, and finally dry it at 110°C to obtain the final product.

[0026] Furthermore, the compressive strength of the concrete after 28 days of curing is 50.23 MPa to 50.37 MPa, and the elastic modulus is 13.2 GPa to 13.3 GPa.

[0027] Furthermore, the splitting tensile strength of the concrete at 28 days was 4.1 MPa.

[0028] Furthermore, the concrete exhibits excellent resistance to chloride ion penetration. After 60 days of salt spray erosion with a 5% NaCl solution, the chloride ion content of the powder sample at a depth of 20 mm from the eroded surface was 0.18%~0.27%.

[0029] This invention also provides an application of low-carbon concrete with a large amount of industrial solid waste in marine environmental construction, port engineering, saline soil foundations and low-carbon energy-saving buildings.

[0030] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0031] This invention prepares a modified material, MIL53(Al-Fe)@SiO2, by in-situ conversion of fly ash and waste aluminum foil, and applies it to a 1:1 solid waste system containing cement fly ash. This method significantly enhances the density of concrete while maintaining high strength and stable mechanical properties above 50 MPa, reducing chloride ion permeability from 0.34% to 0.18%, a reduction of 47.1%. This invention not only achieves high-value utilization and low-carbon emission reduction of industrial solid waste, but also significantly improves the durability of concrete in harsh environments, demonstrating significant environmental and engineering application value. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. The illustrative embodiments and descriptions of this invention are only used to explain this invention and are not intended to limit this invention.

[0033] The main components of fly ash in this invention are CaO 35.5%, SiO2 38.9%, Al2O3 13.4%, Fe2O3 4.6%, and MgO 2.8% by mass.

[0034] The preparation method of MIL53(Al-Fe)@SiO2 in this invention is as follows:

[0035] Fly ash and waste aluminum foil were washed with double-distilled water and dried in a hot air oven at 110°C. Then, a mixture of washed fly ash and aluminum foil (fly ash to aluminum foil weight ratio of 1:0.6) was mixed with ferric chloride at different weight ratios, resulting in a mixture ratio of 0.625:0.375:5 after the addition of ferric chloride. This mixture was then mixed with 35% HNO3 and boiled at 130°C for 45 minutes to convert the alumina and ferric chloride present therein into the corresponding aluminum nitrate and ferric nitrate, respectively. After boiling, the mixture was dried, and terephthalic acid was added at a 1:1 weight ratio, then dispersed in a DMF:distilled water volume ratio of 1:2. The mixture was then stirred continuously at 40°C for 1 hour. After stirring, the mixture was placed in a stainless steel closed high-pressure reactor lined with polytetrafluoroethylene and kept at 150°C for 72 hours. The reactor was then cooled to room temperature. After cooling, the mixture was repeatedly washed with ultrapure water and ethanol to remove unreacted terephthalic acid and excess DMF; the washed sample was dried in a hot air oven at 110°C to obtain MIL53(Al-Fe)@SiO2.

[0036] Example 1

[0037] A low-carbon concrete with high admixture of industrial solid waste comprises, by weight: 170 parts cement, 170 parts fly ash, fine aggregate, 1000 parts coarse aggregate, 132 parts water, 1 part polycarboxylate superplasticizer, and 1 part MIL53(Al-Fe)@SiO2; wherein the coarse aggregate is crushed stone with a particle size distribution between 10 and 20 mm, and the fine aggregate is river sand with a particle size distribution between 2 and 4.5 mm.

[0038] The preparation method of the high-volume industrial solid waste low-carbon concrete is as follows: first, add all dry materials and dry mix for 60 seconds; then add mixing water containing water-reducing agent and continue mixing to obtain the final product.

[0039] Example 2

[0040] A low-carbon concrete with high admixture of industrial solid waste comprises, by weight: 170 parts cement, 170 parts fly ash, fine aggregate, 1000 parts coarse aggregate, 132 parts water, 1 part polycarboxylate superplasticizer, and 2 parts MIL53(Al-Fe)@SiO2; wherein the coarse aggregate is crushed stone with a particle size distribution between 10 and 20 mm, and the fine aggregate is river sand with a particle size distribution between 2 and 4.5 mm.

[0041] The preparation method of the high-volume industrial solid waste low-carbon concrete is as follows: first, add all dry materials and dry mix for 60 seconds; then add mixing water containing water-reducing agent and continue mixing to obtain the final product.

[0042] Example 3

[0043] A low-carbon concrete with high admixture of industrial solid waste comprises, by weight: 170 parts cement, 170 parts fly ash, fine aggregate, 1000 parts coarse aggregate, 132 parts water, 1 part polycarboxylate superplasticizer, and 3 parts MIL53(Al-Fe)@SiO2; wherein the coarse aggregate is crushed stone with a particle size distribution between 10 and 20 mm, and the fine aggregate is river sand with a particle size distribution between 2 and 4.5 mm.

[0044] The preparation method of the high-volume industrial solid waste low-carbon concrete is as follows: first, add all dry materials and dry mix for 60 seconds; then add mixing water containing water-reducing agent and continue mixing to obtain the final product.

[0045] Example 4

[0046] A low-carbon concrete with high admixture of industrial solid waste comprises, by weight: 170 parts cement, 170 parts fly ash, fine aggregate, 1000 parts coarse aggregate, 132 parts water, 1 part polycarboxylate superplasticizer, and 4 parts MIL53(Al-Fe)@SiO2; wherein the coarse aggregate is crushed stone with a particle size distribution between 10 and 20 mm, and the fine aggregate is river sand with a particle size distribution between 2 and 4.5 mm.

[0047] The preparation method of the high-volume industrial solid waste low-carbon concrete is as follows: first, add all dry materials and dry mix for 60 seconds; then add mixing water containing water-reducing agent and continue mixing to obtain the final product.

[0048] Example 5

[0049] A low-carbon concrete with high admixture of industrial solid waste comprises, by weight: 170 parts cement, 170 parts fly ash, fine aggregate, 1000 parts coarse aggregate, 132 parts water, 1 part polycarboxylate superplasticizer, and 5 parts MIL53(Al-Fe)@SiO2; wherein the coarse aggregate is crushed stone with a particle size distribution between 10 and 20 mm, and the fine aggregate is river sand with a particle size distribution between 2 and 4.5 mm.

[0050] The preparation method of the high-volume industrial solid waste low-carbon concrete is as follows: first, add all dry materials and dry mix for 60 seconds; then add mixing water containing water-reducing agent and continue mixing to obtain the final product.

[0051] Comparative Example 1

[0052] A type of low-carbon concrete with high dosage of industrial solid waste comprises, by weight: 170 parts cement, 170 parts fly ash, fine aggregate, 1000 parts coarse aggregate, 132 parts water, and 1 part polycarboxylate superplasticizer; wherein the coarse aggregate is crushed stone with a particle size distribution between 10 and 20 mm, and the fine aggregate is river sand with a particle size distribution between 2 and 4.5 mm.

[0053] The preparation method of the high-volume industrial solid waste low-carbon concrete is as follows: first, add all dry materials and dry mix for 60 seconds; then add mixing water containing water-reducing agent and continue mixing to obtain the final product.

[0054] Test case

[0055] Concrete was poured into standard molds and thoroughly compacted on a vibrating table. The molds were removed 24 hours after molding, and the specimens were immediately transferred to a standard curing room for curing until the specified test age. All mechanical property tests were performed on a universal testing machine at 28 days of age. Each test group contained at least three valid specimens, and the average value was taken. Mechanical properties were tested according to the national standard GB / T 50081-2019, with the elastic modulus controlled by micro-strain gauges and measured under cyclic loading and unloading at 40% of the axial compressive strength.

[0056] Chloride ion content test: After demolding, the specimens were placed in a standard curing chamber at a temperature of (20±1)℃ and a relative humidity of (95±1)% for 60 days. After curing, the specimens were air-dried naturally, and five outer surfaces of the specimens were sealed with epoxy resin, leaving only one side as the chloride ion erosion surface to ensure that the chloride ions in the concrete would erode in a one-dimensional manner later. The treated specimens were then placed in a salt spray chamber for salt spray testing. The salt spray was generated by a 5% NaCl solution, the temperature inside the salt spray chamber was (30±2)℃, and the salt spray deposition rate was 0.125~0.025mL / (h·cm2). After the salt spraying time is specified, the specimens are removed, the epoxy resin sealing layer on the surface of the concrete specimens is peeled off, and then they are placed in an oven at 105℃ for 6 hours to dry. Subsequently, the dried specimens are ground into powder layer by layer from the eroded surface inward using a grinding mill. A layer of powder sample is taken every 2 mm within a depth of 20 mm from the eroded surface, and the obtained powder sample is passed through a 0.16 mm sieve. The chloride ion content is measured by ion-selective electrode method.

[0057] Table 1 Performance Tests

[0058] Example 1 50.23 13.2 4.1 0.27 Example 2 50.34 13.2 4.1 0.24 Example 3 50.36 13.3 4.1 0.19 Example 4 50.37 13.3 4.1 0.18 Example 5 50.31 13.3 4.1 0.18 Comparative Example 1 50.21 13.2 4.1 0.34

[0059] A detailed comparative analysis of the performance test data recorded in Table 1 shows that in a high-volume industrial solid waste low-carbon concrete system with equal amounts of cement and fly ash (170 parts each), the comprehensive performance of the concrete exhibits a significant optimization trend by introducing different weight parts of MIL53 (Al-Fe)@SiO2 modifier. The specific fluctuations of various indicators are as follows:

[0060] Regarding the key compressive strength indicator, Comparative Example 1, without the added modifier, had a compressive strength test value of 50.21 MPa. As the MIL53(Al-Fe)@SiO2 doping amount increased from 1 part to 4 parts, the compressive strength values ​​of Examples 1, 2, 3, and 4 showed a stepwise increase, reaching 50.23 MPa, 50.34 MPa, 50.36 MPa, and the highest in the group at 50.37 MPa, respectively. When the doping amount was further increased to 5 parts, the compressive strength value showed a slight decrease, with a measured result of 50.31 MPa, but still approximately 0.10 MPa higher than Comparative Example 1.

[0061] Regarding deformation and tensile properties, the data exhibited extremely strong stability. The elastic modulus of Comparative Example 1, Example 1, and Example 2 remained at 13.2 GPa, while when the modifier dosage reached 3 parts or more, the elastic modulus values ​​all uniformly increased to 13.3 GPa, an increase of 0.1 GPa compared to the baseline group. Meanwhile, the splitting tensile strength test results of all examples were completely consistent with those of Comparative Example 1, all at 4.1 MPa, indicating that the addition of the modifier, while improving density, did not adversely affect the brittle characteristics of the concrete.

[0062] Comparative Example 1 showed a chloride ion content as high as 0.34% after salt spray testing. In contrast, the example groups with added modifiers exhibited extremely strong anti-permeation capabilities: the chloride ion content in Example 1 decreased to 0.27%, a reduction of 20.59%; in Example 2, it further decreased to 0.24%; and in Example 3, it decreased significantly to 0.19%. When the dosage was increased to 4 and 5 parts, the chloride ion content reached the lowest value of 0.18% in both groups, a decrease of 0.16% in absolute terms compared to the 0.34% in Comparative Example 1, representing a relative reduction of 47.06%.

[0063] In summary, through comparison of experimental data, it can be clearly observed that the introduction of MIL53(Al-Fe)@SiO2 enables concrete to maintain a high strength level of over 50 MPa, while optimizing the elastic modulus through numerical fine-tuning and significantly improving its resistance to chloride ion attack. In particular, when the admixture dosage is 4 parts, the data in all dimensions reach or approach the optimal peak value.

[0064] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A low-carbon concrete with high admixture of industrial solid waste, characterized in that, By weight, its components include: cement: 170 parts; fly ash: 170 parts; fine aggregate: 600-800 parts; coarse aggregate: 1000 parts; water: 132 parts; polycarboxylate superplasticizer: 1 part; modified material MIL53(Al-Fe)@SiO2: 1-5 parts.

2. The low-carbon concrete with high admixture of industrial solid waste according to claim 1, characterized in that: The main components and their mass percentages of the fly ash are: CaO 35.5%, SiO2 38.9%, Al2O3 13.4%, Fe2O3 4.6%, and MgO 2.8%.

3. The low-carbon concrete with high admixture of industrial solid waste according to claim 1, characterized in that: The coarse aggregate is crushed stone with a particle size distribution between 10 and 20 mm; the fine aggregate is river sand with a particle size distribution between 2 and 4.5 mm.

4. The low-carbon concrete with high admixture of industrial solid waste according to claim 1, characterized in that: The preferred amount of the modified material MIL53(Al-Fe)@SiO2 is 3 to 5 parts.

5. The method for preparing low-carbon concrete with high admixture of industrial solid waste according to claim 1, characterized in that, Includes the following steps: S1. Weigh out cement, fly ash, fine aggregate, coarse aggregate and modified material MIL53(Al-Fe)@SiO2 according to the proportion, and put them into the mixer for mixing; S2. Mix the polycarboxylate superplasticizer with water until homogeneous to obtain a mixing solution; S3. Add the mixing liquid obtained in step S2 to the dry material in step S1, and continue stirring until uniform to obtain the high-volume industrial solid waste low-carbon concrete.

6. The preparation method of the modified material MIL53(Al-Fe)@SiO2 in low-carbon concrete with high admixture of industrial solid waste according to claim 1, characterized in that, Includes the following steps: S21. After washing, fly ash and waste aluminum foil are dried at 110°C; S22. Mix the dried fly ash, aluminum foil and ferric chloride, wherein the weight ratio of fly ash to aluminum foil is 1:0.6, and the weight ratio of the three after adding ferric chloride is 0.625:0.375:5; S23. Add a 35% HNO3 solution to the above mixture and boil at 130°C for 45 minutes to convert aluminum oxide and ferric chloride into aluminum nitrate and ferric nitrate in situ. S24. After boiling, dry the mixture, add terephthalic acid at a weight ratio of 1:1, and then disperse it in a mixed solvent of DMF and distilled water, wherein the volume ratio of DMF to distilled water is 1:

2. S25. After stirring continuously at 40°C for 1 hour, transfer to a stainless steel high-pressure reactor and maintain at 150°C for 72 hours; S26. After the reaction vessel has cooled to room temperature, wash it repeatedly with ultrapure water and ethanol, and finally dry it at 110°C to obtain the final product.

7. The low-carbon concrete with high admixture of industrial solid waste according to claim 1, characterized in that: The compressive strength of the concrete after 28 days of curing is 50.23 MPa to 50.37 MPa, and the elastic modulus is 13.2 GPa to 13.3 GPa.

8. The low-carbon concrete with high admixture of industrial solid waste according to claim 1, characterized in that: The splitting tensile strength of the concrete at 28 days was 4.1 MPa.

9. The low-carbon concrete with high admixture of industrial solid waste according to claim 1, characterized in that: This concrete exhibits excellent resistance to chloride ion penetration. After 60 days of salt spray erosion with a 5% NaCl solution, the chloride ion content of the powder sample at a depth of 20 mm from the eroded surface was 0.18%~0.27%.

10. The application of a high-volume industrial solid waste low-carbon concrete according to any one of claims 1-4 in marine environmental construction, port engineering, saline soil foundation and low-carbon energy-saving building fields.