High-ductility cement-based composite material based on lead-zinc tailings as well as preparation method and application of high-ductility cement-based composite material

Abstract

The invention discloses a high-ductility cement-based composite material based on lead-zinc tailings as well as a preparation method and application of the high-ductility cement-based composite material. The high-ductility cement-based composite material comprises the following components in percentage by mass: 20-25% of cement, 20-25% of fly ash, 5-8% of lead-zinc tailings powder, 5-8% of silica fume, 25-30% of quartz sand, 10-15% of water, 0.1-0.4% of a polycarboxylic acid water reducing agent with the water reducing rate being greater than or equal to 25% and 0.22-1.32% of PE (polyethylene) fibers. Wherein the lead-zinc tailing powder comprises the following components: dolomite, pyrite, iron oxide and gypsum. The industrial solid waste lead-zinc tailings are used as main raw materials, the obtained high-ductility cement-based composite material is resistant to sulfate corrosion, and the compressive strength is improved. According to the method, efficient resource utilization of the lead-zinc tailings is achieved, the production cost and carbon emission are reduced, and a new way is provided for development of green low-carbon building materials.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of building materials, and particularly relates to a high-ductility cement-based composite material based on lead-zinc tailings as well as a preparation method and application thereof. BACKGROUND

[0002] With the rapid development of the construction industry, traditional cement-based materials (such as ordinary concrete) have been difficult to meet the needs of complex engineering environments due to their brittleness, poor crack resistance, insufficient durability and other defects. As a new type of material with high toughness and multi-crack characteristics, engineering cement-based composite materials (ECC) significantly improve the tensile properties (ultimate tensile strain ≥ 3%) through fiber toughening. PE fibers inhibit crack propagation by bridging cracks, so that the material produces a large number of micro-cracks instead of single-crack fracture when subjected to tension, thereby achieving high ductility. However, traditional ECC relies on high-cost quartz sand and a large amount of cement, and has high production energy consumption and carbon emissions.

[0003] Solid waste-based ECC refers to a high-ductility cement-based composite material (ECC) prepared by using industrial solid waste as the main raw material. With the emphasis on environmental protection and resource recycling, solid waste-based ECC, as a low-carbon and environmentally friendly material, has attracted more attention and application. At present, various industrial solid wastes are used to prepare ECC, for example, fly ash, silica fume, desulfurization gypsum, etc. are used to replace part of the cement to improve the mechanical properties of ECC.

[0004] The accumulation of industrial solid waste such as lead-zinc tailings is becoming increasingly serious, and its chemical composition (such as CaO, Fe2O3, MgO) and mineral composition (dolomite, pyrite, etc.) have not been effectively utilized as resources. If such tailings are directly stored, not only will it occupy land, but also the heavy metal components may cause environmental pollution, and therefore it is urgent to develop an economic and efficient recycling technology.

[0005] The chemical characteristics of lead-zinc tailings are similar to those of cement raw materials, and they are in the form of powder or fine sand, so they can replace the raw materials of cement. There have been related reports on using lead-zinc tailings to replace part of the cement production raw materials to prepare cement clinker, but in the process of preparing cement by incorporating tailings, the original volatile heavy metal elements in the lead-zinc tailings will be emitted through flue gas due to high-temperature calcination, causing heavy metal pollution.

[0006] Currently, there are also reports that lead-zinc tailings are used as fine admixtures for concrete, such as disclosed in “Influence of Lead-zinc Tailings Powder on the Performance of Cement Mortar” (Journal of Suzhou University, October 2015, Vol. 30, No. 10, p100-103), which discloses that lead-zinc tailings are mixed in P.C32.5 composite cement, and the mortar ingredients are cement, lead-zinc tailings powder, sand and water, it is found that different mixing amounts and different particle sizes of lead-zinc tailings have an effect on the compressive strength, and the mixing of lead-zinc tailings will reduce the compressive strength. For example, “Preparation of High-strength Concrete Using Lead-zinc Tailings and Slag Powder from a Mine in Fujian” (Metal Mines, January 2015, p176-180) discloses the influence of adding different proportions of lead-zinc tailings (see Table 1 for components), slag and gypsum to cement on the performance of concrete, and the mortar ingredients are cement, sand, gravel, water reducing agent, water and lead-zinc tailings + slag + gypsum, it is found that the combination of lead-zinc tailings + slag + gypsum can improve the compressive strength.

[0007] Table 1 Chemical composition analysis of lead-zinc tailings However, the concrete containing lead-zinc tailings reported so far has not been studied for its resistance to sulfate attack, and the traditional ECC still lacks resistance to sulfate attack and chloride ion penetration, especially in marine engineering and saline-alkali environment, which is prone to durability degradation, so it is urgent to develop cement composite materials that can resist sulfate attack.

[0008] It should be noted that the information disclosed in the above background section is only used to strengthen the understanding of the background of the present disclosure, and therefore can include information that does not constitute prior art known to those of ordinary skill in the art. SUMMARY

[0009] The purpose of the present application is to provide a lead-zinc tailings-based high-ductility cement-based composite material and its preparation method and application. The present application uses industrial solid waste lead-zinc tailings as the main raw material, and the obtained high-ductility cement-based composite material is resistant to sulfate attack and has improved compressive strength. The present application realizes efficient resource utilization of lead-zinc tailings, reduces production cost and carbon emissions, and provides a new way for the development of green and low-carbon building materials.

[0010] To achieve the above object, the application provides a high ductility cement-based composite material based on lead-zinc tailings, which comprises the following components in mass fraction: cement 20-25%, fly ash 20-25%, lead-zinc tailing powder 5-8%, silica fume 5-8%, quartz sand 25-30%, water 10-15%, polycarboxylate superplasticizer with water-reducing rate ≥25% 0.1-0.4%, and PE fiber 0.22-1.32%; wherein the lead-zinc tailing powder comprises the following components in mass fraction: 63% dolomite (CaMg(CO3)2), 24% pyrite (FeS2), 12% gypsum (CaSO4·2H2O), and 1% sphalerite.

[0011] Preferably, the high ductility cement-based composite material comprises the following components in mass fraction: cement 20-23%, fly ash 24-25%, lead-zinc tailing powder 5-8%, silica fume 5-6%, quartz sand 27-28%, water 13-14%, polycarboxylate superplasticizer with water-reducing rate ≥25% 0.3%, and PE fiber 0.5%.

[0012] Preferably, the particle size of the lead-zinc tailing powder is 100 μm.

[0013] Preferably, the cement is ordinary portland cement.

[0014] More preferably, the ordinary portland cement is selected from P.O 42.5 ordinary portland cement.

[0015] Preferably, the fly ash is first-grade fly ash; or / and, the diameter of the PE fiber is 30 μm, the length is 15 mm, the elastic modulus is 132 Gpa, and the density is 1.02 g / cm -3 .

[0016] The second object of the application is to provide a preparation method of the high ductility cement-based composite material based on lead-zinc tailings, which comprises the following steps: (S1) dry mixing cement, fly ash, silica fume, quartz sand and lead-zinc tailing powder to ensure uniform distribution of the materials, to obtain dry mixture; (S2) adding water and polycarboxylate superplasticizer in the dry mixture, and continuously stirring until the slurry fluidity reaches 150-180 mm; (S3) adding PE fiber in stages, and controlling the stirring speed ≤300 r / min to avoid fiber agglomeration, to obtain the high ductility cement-based composite material based on lead-zinc tailings.

[0017] Preferably, the lead-zinc tailings powder is obtained by coarse crushing the lead-zinc tailings to obtain particles with a particle size of ≤10 mm, and then ball milling by a ball mill to obtain lead-zinc tailings powder with a particle size of 100 μm; or / and, the rotation speed of the dry mixing is 160-170 r / min; or / and, the PE fibers are added in three stages, and the amount of each stage is equal.

[0018] A third object of the present application is to provide the use of the lead-zinc tailings-based high-ductility cement-based composite material in a sulfate attack environment.

[0019] Preferably, the lead-zinc tailings-based high-ductility cement-based composite material is applied in the fields of marine engineering, saline-alkali infrastructure, bridge repair or low-carbon building structure.

[0020] The lead-zinc tailings-based high-ductility cement-based composite material, the preparation method and the use thereof have the following advantages: (1) The present application uses industrial solid waste lead-zinc tailings as the main raw material, and is prepared by partially replacing quartz sand and cementitious materials in traditional ECC. The dolomite (CaMg(CO3)2) and gypsum (CaSO4·2H2O) in the lead-zinc tailings inhibit sulfate attack through a chemical stability reaction, and the pyrite (FeS2) and iron oxide can chemically adsorb chloride ions, significantly reducing the risk of steel corrosion. At the same time, the carbonate provides nucleation sites in the cement-based material at an early stage, accelerates hydration and promotes CO2 absorption, and improves early strength and carbon dioxide absorption rate. The compressive strength of the material is above 45 MPa, the ultimate tensile strain is ≥3.5%, and the sulfate immersion strength loss rate is <5%;

[0021] (2) The efficient utilization of tailings and the reduction of carbon emissions in the present application are derived from the synergistic optimization of the multi-component mineral properties and the low-carbon process. The lead-zinc tailings are rich in dolomite (CaMg(CO3)2 and CaO), which can be processed to 100 μm particle size after ball milling and used as fine aggregate to replace 30-50% of quartz sand, reducing the environmental burden of natural sand mining. At the same time, the active CaO and Al2O3 in the tailings partially replace cement (cement reduction 5-8%) during the hydration process, reducing the high carbon emissions of cement production from the source (each ton of cement reduction corresponds to a reduction of 0.8 tons of CO2). Each cubic meter of material can sequester 100-150 kg of carbon, and the carbon emissions of the whole life cycle are reduced by 25% compared with traditional ECC, achieving the dual benefits of resource utilization and low carbon;

[0022] (3) The present application significantly improves the mechanical properties of the tailings through the micro-aggregate effect of the tailings. The tailings particles act as micro-aggregates to fill the pores of the matrix, and the increase in density makes the 28-day compressive strength above 45 MPa, while the nucleation effect of carbonate (CaMg(CO3)2) accelerates the formation of early C-S-H gel, and the 3-day strength is increased by 10-20%;

[0023] (4) This invention optimizes durability through mineral chemical reactions and microstructure regulation. For sulfate-eroded environments, dolomite (CaMg(CO3)2) reacts with sulfate ions (SO42-) 2- Ion interactions exist, preventing the formation of expandable ettringite (AFt). The strength loss after soaking in a 5% sodium sulfate solution for 90 days is only about 5%. Meanwhile, pyrite (FeS2) and Cl in the tailings... - Chemisorption occurs, and hydroxyl groups (-OH) on the surface of the iron-containing gel fix Cl through coordination bonds. - The nanoscale gel pores formed by carbon curing work together to block the migration path of intermolecular molecules, which can extend the service life of the structure. Attached Figure Description

[0024] Figure 1 This is a dimensional diagram of the standard dog bone specimen used for the tensile property test in Experiment Example 2 of this invention. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] It should be noted that: Unless otherwise specified in the examples, standard conditions or conditions recommended by the manufacturer should be followed. Instruments whose manufacturers are not specified are all commercially available products. Raw materials and reagents whose manufacturers are not specified are all commercially available goods or can be prepared using known methods.

[0027] In this invention, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are used only for simplicity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0028] The features mentioned in this invention can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification, provided that there is no contradiction in the combination of these features. Each feature disclosed in the specification can be replaced by any alternative feature that provides the same, equivalent, or similar purpose. Therefore, unless otherwise specified, the disclosed features are merely general examples of equivalent or similar features.

[0029] The raw materials used in the following embodiments and comparative examples are as follows: The cement is P.O 42.5 ordinary portland cement; the fly ash is first grade fly ash; the water reducing agent is ZJ-PC8020 type polycarboxylic acid high performance water reducing agent purchased from Hubei Zhaojia Material Co., Ltd.; the diameter of the PE fiber is 30 microns, the length is 15 mm, the elastic modulus is 132 Gpa, and the density is 1.02 g·cm -3 .

[0030] The water reducing agent is polycarboxylic acid high performance water reducing agent with a water reducing rate of 25% or more; the diameter of the PE fiber is 30 microns, the length is 15 mm, the elastic modulus is 132 Gpa, and the density is 1.02 g·cm -3 .

[0031] The lead-zinc tailing powder used in each embodiment of the present application is subjected to chemical composition analysis by XRF testing, as shown in Table 2.

[0032] Table 2 Chemical composition of the lead-zinc tailing powder of the present application Example 1 A lead-zinc tailing based high ductility cement composite material (ECC) includes the following components by mass percentage: Cement 22.64%, fly ash 24.51%, lead-zinc tailing powder 5.24%, silica fume 6.13%, quartz sand 27.24%, water 13.44%, polycarboxylic acid high performance water reducing agent 0.3%, and PE fiber 0.5%.

[0033] The mineral components of the lead-zinc tailing powder include, by mass percentage, 63% dolomite (CaMg(CO3)2), 24% pyrite (FeS2), 12% gypsum (CaSO4·2H2O), 1% sphalerite, and a particle size of 100 microns.

[0034] The preparation method of the lead-zinc tailing based high ductility cement composite material of the present embodiment comprises the following steps: (1) Coarse crushing of the lead-zinc tailing is performed using a jaw crusher to obtain particles with a particle size of 10 mm or less; (2) The crushed lead-zinc tailing is transferred to a ball mill, and ball milling is performed at a ball-to-material ratio of 3:1 and a rotation speed of 30 r / min for 90 minutes to obtain lead-zinc tailing powder with a particle size of 100 microns; (3) The cement, fly ash, silica fume, quartz sand, and lead-zinc tailing powder are proportionally fed into a forced mixer (capacity 500 L) and dry mixed at a rotation speed of 165 r / min for 10 minutes to ensure uniform distribution of the materials; (4) Water and polycarboxylic acid water reducing agent are slowly added to the dry mixed material, the rotation speed is adjusted to 300 r / min, and continuous stirring is performed for 5 minutes until the slurry flow degree reaches 150 mm; (5) Add PE fiber in three stages (2 minutes interval between each stage), control stirring speed 200 r / min, the amount of fiber added in each stage is 1 / 3 of the total mass of PE fiber, to avoid fiber agglomeration, and obtain a high ductility cement-based composite material based on lead-zinc tailings.

[0035] Example 2 A high ductility cement-based composite material (ECC) based on lead-zinc tailings, according to the mass percentage of its raw materials, includes the following components: Cement 21.15%, fly ash 24.51%, lead-zinc tailings powder 6.73%, silica fume 6.13%, quartz sand 27.24%, water 13.44%, and polycarboxylic acid high-performance water reducing agent 0.3%, PE fiber 0.5%.

[0036] Among them, the mineral components of lead-zinc tailings powder include, by mass percentage: 63% dolomite (CaMg(CO3)2), 24% pyrite (FeS2), 12% gypsum (CaSO4·2H2O), 1% sphalerite, and particle size 100 μm.

[0037] The preparation method of the high ductility cement-based composite material based on lead-zinc tailings of the present embodiment is basically the same as that of Example 1, except that the amounts of the raw materials are different, and the mass percentages of the raw materials in the present embodiment can be added.

[0038] Example 3 A high ductility cement-based composite material (ECC) based on lead-zinc tailings, according to the mass percentage of its raw materials, includes the following components: Cement 20.46%, fly ash 24.51%, lead-zinc tailings powder 7.42%, silica fume 6.13%, quartz sand 27.24%, water 13.44%, and polycarboxylic acid high-performance water reducing agent 0.3%, PE fiber 0.5%.

[0039] Among them, the mineral components of lead-zinc tailings powder include, by mass percentage: 63% dolomite (CaMg(CO3)2), 24% pyrite (FeS2), 12% gypsum (CaSO4·2H2O), 1% sphalerite, and particle size 100 μm.

[0040] The preparation method of the high ductility cement-based composite material based on lead-zinc tailings of the present embodiment is basically the same as that of Example 1, except that the amounts of the raw materials are different, and the mass percentages of the raw materials in the present embodiment can be added.

[0041] Comparative Example 1 A cement-based composite material, according to the mass percentage of its raw materials, includes the following components: Cement 27.88%, fly ash 24.51%, silica fume 6.13%, quartz sand 27.24%, water 13.44%, and polycarboxylate high-performance water reducing agent 0.3%, PE fiber 0.5%.

[0042] The preparation method of the cement-based composite material of the present embodiment is basically the same as that of Example 1, except that the lead-zinc tailing powder is not added, and steps (1)-(2) of Example 1 are not performed; in step (3), the cement, fly ash, etc. are added into the forced stirrer in proportion.

[0043] Experimental Example 1: Compression strength performance test The cement-based composite materials prepared in the above examples and comparative examples were injected into a mold and mechanically vibrated to compact (frequency 50 Hz, time length 60 s), demolded after standing for 24 h, and cured under standard conditions: temperature 20±2℃, relative humidity ≥95% in a constant temperature and humidity chamber for 3 d or 28 d, with daily monitoring of the temperature and humidity fluctuation range (±1℃, ±3%), and the compressive strength of the cement stone was measured at 3 d or 28 d.

[0044] The compressive strength performance data of the samples prepared in Examples 1-3 and the comparative example after curing are shown in Table 4. As can be seen from Table 4, the lead-zinc tailing powder as microaggregate fills the pores of the matrix, and the improvement of the compactness makes the 28-day compressive strength reach more than 45 MPa, while the nucleation effect of the carbonate (CaMg(CO3)2) accelerates the formation of early C-S-H gel, and the 3-day strength is increased by 10-18%.

[0045] Table 4: Compressive strength performance data of cement stone Experimental Example 2: Tensile performance test Standard dog bone test pieces were used, and the size of the test piece was as shown in Figure 1 The specific test process was as follows: Four test pieces were cast for each group, demolded after standing at room temperature for 24 h, and cured in a standard curing room at a temperature of 20±2℃ and a humidity of ≥95% for 28 days. A 20 kN universal testing machine was used, and the displacement control mode was adopted. The load mode was loaded (10 N / s rate), unloaded to 60 N after loading from 0 N to 300 N, and cycled 3 times to eliminate the gap between the clamps. The displacement rate was 0.5 mm / min, and the test was stopped when the displacement reached 20 mm or the load decreased to 60% of the peak value.

[0046] Table 5: Tensile performance test data table The tensile test shows that the ultimate tensile strain of the ECC test piece doped with the lead-zinc tailing powder of the application is 3.5-4.1%, and the typical multi-crack cracking characteristics (crack number 10-15 / m, width ≤80 μm) are presented, which is significantly better than the brittle fracture (strain 0.02%) of the control example. This is due to the physical densification of the tailing powder of the application, the micron-sized particle filling the matrix pores, and the reduction of defect concentration; at the same time, the deposition of the carbonate microcrystal generated by the dissolution of dolomite at the fiber-matrix interface forms a nano-enhanced transition layer, and the chemical bonding force between the PE fiber and the matrix is improved; the above-mentioned effects make the material produce continuous strain hardening through efficient fiber bridging when subjected to tension, and realize the ductile response.

[0047] Experimental Example 3: Sulfate Resistance Performance Test According to the method of Experimental Example 1, the cured test block is immersed in a sodium sulfate solution for 90 days, and the corrosion environment is a 5% Na2SO4 solution. In order to ensure the relative stability of the solution concentration, the solution is re-adjusted and replaced every 30 days, and the surface of the solution is kept above the surface of the test piece by more than 2 cm. The compressive strength of the cement stone without immersion and immersed for 90 days is determined.

[0048] The compressive strength of Examples 1-3 and the control example at different corrosion times is shown in Table 6. As can be seen from Table 6, the strength loss rate after 90 days of immersion in a 5% sodium sulfate solution is only about 5%, which may be due to the ion interaction between dolomite (CaMg(CO3)2) and sulfate ions (SO4 2- ), which avoids the generation of expansive ettringite (AFt).

[0049] Table 6: Compressive strength data of cement stone after sulfate corrosion In summary, the lead-zinc tailings are used as raw materials to prepare the application, which improves the mechanical properties of the cement stone, and is suitable for marine engineering, saline-alkali infrastructure, bridge repair and low-carbon building structure, and is especially recommended for durability requirements in sulfate corrosion environments.

[0050] Although the content of the application has been described in detail by the above preferred embodiments, it should be recognized that the above description should not be considered as a limitation of the application. After reading the above content, various modifications and alternatives of the application will be obvious to those skilled in the art. Therefore, the protection scope of the application should be defined by the appended claims.

Claims

1. A high-ductility cement-based composite material based on lead-zinc tailings, characterized in that, This high-ductility cement-based composite material contains the following components by mass fraction: 20-25% cement, 20-25% fly ash, 5-8% lead-zinc tailings powder, 5-8% silica fume, 25-30% quartz sand, 10-15% water, 0.1-0.4% polycarboxylate superplasticizer with a water reduction rate ≥25%, and 0.22-1.32% PE fiber; The lead-zinc tailings powder contains the following components by mass fraction: 63% dolomite, 24% pyrite, 12% gypsum, and 1% sphalerite.

2. The high-ductility cement-based composite material based on lead-zinc tailings according to claim 1, characterized in that, The high-ductility cement-based composite material contains the following components by mass fraction: 20-23% cement, 24-25% fly ash, 5-8% lead-zinc tailings powder, 5-6% silica fume, 27-28% quartz sand, 13-14% water, 0.3% polycarboxylate superplasticizer with a water reduction rate of ≥25%, and 0.5% PE fiber.

3. The high-ductility cement-based composite material based on lead-zinc tailings according to claim 1, characterized in that, The particle size of the lead-zinc tailings powder is 100 μm.

4. The high-ductility cement-based composite material based on lead-zinc tailings according to claim 1, characterized in that, The cement used is ordinary Portland cement.

5. The high-ductility cement-based composite material based on lead-zinc tailings according to claim 4, characterized in that, The ordinary silicate cement is selected from PO 42.5 ordinary silicate cement.

6. The high-ductility cement-based composite material based on lead-zinc tailings according to claim 1, characterized in that, The fly ash used is Grade I fly ash; Or / and, the PE fiber has a diameter of 30 μm, a length of 15 mm, an elastic modulus of 132 GPa, and a density of 1.02 g / cm³. -3 .

7. The method for preparing a high-ductility cement-based composite material based on lead-zinc tailings as described in any one of claims 1 to 6, characterized in that, The method includes the following steps: (S1) Dry mix cement, fly ash, silica fume, quartz sand and lead-zinc tailings powder to ensure uniform distribution of materials and obtain dry mix; (S2) Add water and polycarboxylate superplasticizer to the dry mixture and continue stirring until the slurry fluidity reaches 150~180mm; (S3) PE fibers are added in stages, and the stirring speed is controlled to ≤300r / min to avoid fiber agglomeration and obtain a high ductility cement-based composite material based on lead-zinc tailings.

8. The preparation method according to claim 7, characterized in that, The lead-zinc tailings powder is obtained by coarsely crushing lead-zinc tailings to obtain particles with a particle size ≤10mm, and then ball milling them to obtain lead-zinc tailings powder with a particle size of 100μm. Or / and, the rotation speed of the dry mixing is 160~170 r / min; Or / and, the PE fibers are added in three stages, with equal amounts added in each stage.

9. The application of the high-ductility cement-based composite material based on lead-zinc tailings as described in any one of claims 1 to 6 in sulfate-eroded environments.

10. The application according to claim 9, characterized in that, The high-ductility cement-based composite material based on lead-zinc tailings is applied in marine engineering, saline-alkali land infrastructure, bridge repair, or low-carbon building structures.

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