A composite cement-based concrete doped with pyrite and wood ash
By simultaneously adding pyrite and wood ash to concrete, the problem of insufficient impact resistance and crack resistance of existing concrete materials is solved, and the overall performance of concrete is improved, especially in terms of early strength and toughness.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- YANBIAN UNIV
- Filing Date
- 2023-12-05
- Publication Date
- 2026-06-26
AI Technical Summary
Existing concrete materials are inadequate in terms of impact resistance, crack resistance, and corrosion resistance. Furthermore, the limited resources of natural river sand have led to a prominent contradiction between the supply and demand of sand for engineering projects. Research on the separate addition of plant ash and pyrite has not yet been conducted in depth.
By simultaneously adding 15% pyrite to replace sand and 15% wood ash to replace fly ash in concrete, a composite cement-based concrete is formed. The passivation effect of wood ash on pyrite improves the toughness and impact resistance of the concrete.
It significantly improves the early strength, compressive strength, tensile strength and elastic modulus of concrete, improves the toughness and crack resistance of concrete, reduces brittleness, and enhances impact resistance, achieving a 1+1>2 effect.
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Figure CN117700171B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of concrete materials for building construction, and in particular to a composite cement-based concrete doped with pyrite and wood ash. Background Technology
[0002] Concrete is one of the most widely used building materials in the world. Due to its high compressive strength and low cost, concrete is widely used in civil engineering. However, concrete suffers from high brittleness, insufficient impact resistance, poor cracking performance, high production energy consumption, and poor corrosion resistance, all of which require solutions. For the sake of human safety, modern engineering demands on the comprehensive performance of concrete materials are increasing year by year. Concrete strength is a crucial parameter in engineering design, ensuring that buildings maintain their designed concrete strength during use; otherwise, a decrease in concrete strength can lead to the failure of part or the entire structure. To meet the safety, durability, economy, and environmental protection requirements of civil engineering, admixtures (such as water-reducing agents) play a significant role as components of concrete and have become an indispensable part of high-performance concrete. They are of great importance in terms of economy, environmental protection, and safety.
[0003] my country is a major agricultural country with abundant agricultural crop resources. However, with the continuous increase in agricultural output, agricultural waste is also increasing. To meet the construction industry's demand for cement, many scholars are searching for cement alternatives. Biomass ash (wood ash) has attracted the attention of civil engineering experts due to its enormous potential. It undoubtedly has great prospects in the field of materials application. However, because there are many types of wood ash, research on wood ash concrete is still in its early stages. Therefore, further exploration of wood ash as a concrete admixture has great application potential.
[0004] In concrete, coarse and fine aggregates account for approximately 70% of the volume. Natural river sand is the main source of fine aggregate in concrete. However, due to the limited total amount and uneven distribution of river sand resources, increasing environmental pressure, and rising transportation costs, the supply and demand contradiction of sand for engineering projects is becoming increasingly prominent. Therefore, in recent years, many scholars have been researching materials suitable as alternatives to natural aggregates. Natural pyrite has a negative Poisson's ratio effect, and due to its unique properties, it has great potential for application in concrete, providing the construction industry with more environmentally friendly and sustainable building materials.
[0005] Chinese patent application CN201410352904.0 discloses a high thermal conductivity concrete, made from the following raw materials in parts by weight: 100-140 parts kyanite, 70-80 parts mullite, 80-100 parts wollastonite, 60-70 parts ceramsite, 8-10 parts sodium fluorosilicate, 4-6 parts hydroxymethyl cellulose, 2-3 parts sodium citrate, 40-50 parts pyrite powder, 15-20 parts chromium carbide powder, 15-20 parts silicon nitride powder, 20-25 parts aluminum nitride powder, 170-190 parts cement, 500-530 parts aggregate, appropriate amount of water, and 21-25 parts additives. The addition of kyanite, mullite, and wollastonite increases the concrete's crack resistance and strength. The addition of chromium carbide powder, silicon nitride powder, and aluminum nitride powder further enhances the concrete's thermal conductivity, durability, and strength.
[0006] Chinese patent application CN202111523110.2 discloses a composite high-strength concrete and its preparation method, comprising the following components by weight: 230-280 parts cement, 200-300 parts high-strength material, 20-60 parts wood ash, 10-15 parts waste fiber, 10-20 parts lignin, 5-15 parts liquid paraffin, 8-30 parts water glass, 5-12 parts water-reducing agent, 120-210 parts water, and 15-25 parts molecular sieve; wherein the high-strength material is a mixture of crushed bricks, waste concrete blocks, and industrial waste. This high-strength concrete exhibits strong impermeability and high compressive strength, making it less prone to cracking under pressure.
[0007] Both types of concrete mentioned above involve the individual addition of wood ash or pyrite. While the individual addition of wood ash or pyrite can indeed enhance the mechanical properties of concrete, the simultaneous addition of both wood ash and pyrite to concrete does not improve its mechanical properties. Furthermore, research on wood ash-pyrite concrete is currently lacking both domestically and internationally. Summary of the Invention
[0008] To address the aforementioned technical problems, this invention provides a composite cement-based concrete doped with pyrite and wood ash.
[0009] To achieve the above objectives, the present invention is implemented according to the following technical solution:
[0010] A composite cement-based concrete doped with pyrite and wood ash, the concrete comprising the following raw materials in parts by weight:
[0011]
[0012] Preferably, the plant ash is corn stalk ash.
[0013] Preferably, the pyrite fine sand is pyrite fine sand with natural negative Poisson's ratio, has a particle size of 1 mm, and a density of 4700 kg / m³.3 .
[0014] Preferably, the fly ash is Class F, Grade I, with a density of 2180 kg / m³. 3 Fineness 10.4%.
[0015] Preferably, the particle size of the crushed stone is 5-20 mm.
[0016] Preferably, the fineness modulus of the sand in the sand washing process is 2.56.
[0017] Preferably, the cement is ordinary Portland cement with a density of 3150 kg / m³. 3 .
[0018] Preferably, the water-reducing agent is a polycarboxylate water-reducing agent.
[0019] Compared with existing technologies, this invention, by simultaneously replacing sand with 15% pyrite in sand and replacing fly ash with 15% wood ash in cement and fly ash in composite cement-based concrete, achieves the greatest improvement in the mechanical properties of concrete. Early strength, cubic compressive strength, tensile strength, and modulus of elasticity are significantly increased. It can be inferred that wood ash-pyrite improves the overall mechanical properties of concrete, and effectively enhances its toughness, impact resistance, and crack resistance. The concrete of this invention exhibits significantly superior mechanical properties compared to the combined mechanical properties of concrete with either wood ash alone or pyrite-based fine sand, demonstrating a 1+1>2 effect. Attached Figure Description
[0020] Figure 1 Three-dimensional diagram of the compressive strength of 7-day wood ash-pyrite cubes.
[0021] Figure 2 Three-dimensional diagram of the compressive strength of 14-day wood ash-pyrite cubes.
[0022] Figure 3 Three-dimensional diagram of the compressive strength of 28-day wood ash-pyrite cubes.
[0023] Figure 4 The effect of wood ash on the compressive strength of cubes in the absence of pyrite.
[0024] Figure 5 The effect of wood ash with 5% pyrite on the compressive strength of cubes.
[0025] Figure 6 The effect of wood ash with 10% pyrite on the compressive strength of cubes.
[0026] Figure 7 The effect of wood ash with 15% pyrite on the compressive strength of cubes.
[0027] Figure 8 The effect of pyrite on the compressive strength of cubes in the absence of plant ash.
[0028] Figure 9 The effect of pyrite with 5% wood ash on the compressive strength of cubes.
[0029] Figure 10 The effect of wood ash with 10% pyrite on the compressive strength of cubes.
[0030] Figure 11 The effect of wood ash with 15% pyrite on the compressive strength of cubes.
[0031] Figure 12 Three-dimensional diagram of the tensile strength of wood ash-pyrite cubes.
[0032] Figure 13 This is a diagram showing the tensile strength of a cubic plant ash-pyrite mixture.
[0033] Figure 14 A three-dimensional diagram of the elastic modulus of plant ash-pyrite concrete.
[0034] Figure 15 This is a diagram showing the compression-tension ratio of plant ash-pyrite concrete.
[0035] Figure 16 The elastic strength ratio diagram of plant ash-pyrite concrete.
[0036] Figure 17 The fitting diagram is for the plant ash-pyrite concrete model.
[0037] Figure 18 This represents the failure mode of ordinary concrete.
[0038] Figure 19 The failure mode of plant ash-pyrite concrete. Detailed Implementation
[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.
[0040] The natural coarse aggregate crushed stone used in the following examples is locally produced crushed stone from Yanji City, with a particle size of 5-20mm; the sand is locally produced washed medium sand from Yanji City, with a fineness modulus of 2.56. The cement is Miaoling brand P·O 42.5 grade ordinary Portland cement from Yanbian Korean Autonomous Prefecture, with a density of 3150kg / m³. 3 The fly ash is Class F, Grade I fly ash supplied by Yanji Guodian Longhua, with a density of 2180 kg / m³. 3The fineness is 10.4%, water requirement ratio is 84%, loss on ignition is 0.36%, and moisture content is 0.1%. The wood ash is provided by Yunhubuxi E-commerce Co., Ltd., and the pH is alkaline. The mixing water is ordinary tap water. The water-reducing agent is a polycarboxylate-based high-performance water-reducing agent produced by Jilin Fang Sheng Co., Ltd., with a dosage of 0.2%. The pyrite fine sand is pyrite fine sand with natural negative Poisson's ratio, sourced from Lingshou County, Shijiazhuang City, Hebei Province, with a particle size of approximately 1 mm and a density of 4700 kg / m³. 3 .
[0041] Comparative Example 1
[0042] The reference concrete includes the following raw materials:
[0043] 438 kg of cement; 109 kg of fly ash; 1182 kg of crushed stone; 506 kg of sand; 7.9 kg of water-reducing agent; 165 kg of water.
[0044] Comparative Example 2
[0045] Concrete made by replacing sand with 5% pyrite as a single dopant in sand includes the following raw materials:
[0046] 438 kg of cement; 109 kg of fly ash; 1182 kg of crushed stone; 480.7 kg of sand; 25.3 kg of pyrite fine sand; 7.9 kg of water-reducing agent; 165 kg of water.
[0047] Comparative Example 3
[0048] Concrete made by replacing sand with 10% pyrite as a single dopant includes the following raw materials:
[0049] 438 kg of cement; 109 kg of fly ash; 1182 kg of crushed stone; 455.4 kg of sand; 50.6 kg of pyrite fine sand; 7.9 kg of water-reducing agent; 165 kg of water.
[0050] Comparative Example 4
[0051] Concrete made by replacing sand with 15% pyrite as a single additive in sand includes the following raw materials:
[0052] 438 kg of cement; 109 kg of fly ash; 1182 kg of crushed stone; 430.1 kg of sand; 75.9 kg of pyrite fine sand; 7.9 kg of water-reducing agent; 165 kg of water.
[0053] Comparative Example 5
[0054] Concrete made by adding 5% wood ash instead of fly ash to cement and fly ash includes the following raw materials:
[0055] 438 kg of cement; 82.05 kg of fly ash; 1182 kg of crushed stone; 506 kg of sand; 27.35 kg of wood ash; 8.0 kg of water-reducing agent; 165 kg of water.
[0056] Comparative Example 6
[0057] Concrete made by adding 10% wood ash instead of fly ash to cement and fly ash includes the following raw materials:
[0058] 438 kg of cement; 54.7 kg of fly ash; 1182 kg of crushed stone; 506 kg of sand; 54.7 kg of wood ash; 8.1 kg of water-reducing agent; 165 kg of water.
[0059] Comparative Example 7
[0060] Concrete made by adding 15% wood ash instead of fly ash to cement and fly ash includes the following raw materials:
[0061] 438 kg of cement; 27.35 kg of fly ash; 1182 kg of crushed stone; 506 kg of sand; 82.05 kg of wood ash; 8.2 kg of water-reducing agent; 165 kg of water.
[0062] Example 1
[0063] The composite cement-based concrete, which uses 5% pyrite as a single dopant in sand to replace sand, and 5% wood ash as a single dopant in cement to replace fly ash, comprises the following raw materials:
[0064] 438 kg of cement; 82.05 kg of fly ash; 1182 kg of crushed stone; 480.7 kg of sand; 25.3 kg of fine pyrite sand; 27.35 kg of wood ash; 8.0 kg of water-reducing agent; 165 kg of water.
[0065] Example 2
[0066] Composite cement-based concrete, which uses 5% pyrite as a single dopant in sand to replace sand, and 10% wood ash as a single dopant in cement to replace fly ash, comprises the following raw materials:
[0067] 438 kg of cement; 54.7 kg of fly ash; 1182 kg of crushed stone; 480.7 kg of sand; 25.3 kg of fine pyrite sand; 54.7 kg of wood ash; 8.1 kg of water-reducing agent; 165 kg of water.
[0068] Example 3
[0069] Composite cement-based concrete, which replaces sand with 5% pyrite in sand and cement with 15% wood ash in fly ash, includes the following raw materials:
[0070] 438 kg of cement; 27.35 kg of fly ash; 1182 kg of crushed stone; 480.7 kg of sand; 25.3 kg of fine pyrite sand; 82.05 kg of wood ash; 8.2 kg of water-reducing agent; 165 kg of water.
[0071] Example 4
[0072] Composite cement-based concrete, which uses 10% pyrite as a single dopant in sand to replace sand, and 5% wood ash as a single dopant in cement to replace fly ash, comprises the following raw materials:
[0073] 438 kg of cement; 82.05 kg of fly ash; 1182 kg of crushed stone; 455.4 kg of sand; 50.6 kg of fine pyrite sand; 27.35 kg of wood ash; 8.0 kg of water-reducing agent; 165 kg of water.
[0074] Example 5
[0075] The composite cement-based concrete, which uses 10% pyrite as a single dopant in sand to replace sand, and 10% wood ash as a single dopant in cement to replace fly ash, comprises the following raw materials:
[0076] 438 kg of cement; 54.7 kg of fly ash; 1182 kg of crushed stone; 455.4 kg of sand; 50.6 kg of fine pyrite sand; 54.7 kg of wood ash; 8.1 kg of water-reducing agent; 165 kg of water.
[0077] Example 6
[0078] The composite cement-based concrete, which uses 10% pyrite as a single dopant in sand to replace sand, and 15% wood ash as a single dopant in cement to replace fly ash, comprises the following raw materials:
[0079] 438 kg of cement; 27.35 kg of fly ash; 1182 kg of crushed stone; 455.4 kg of sand; 50.6 kg of fine pyrite sand; 82.05 kg of wood ash; 8.2 kg of water-reducing agent; 165 kg of water.
[0080] Example 7
[0081] Composite cement-based concrete, which uses 15% pyrite as a substitute for sand in sand and 5% wood ash as a substitute for fly ash in cement and fly ash, comprises the following raw materials:
[0082] 438 kg of cement; 82.05 kg of fly ash; 1182 kg of crushed stone; 430.1 kg of sand; 75.9 kg of fine pyrite sand; 27.35 kg of wood ash; 8.0 kg of water-reducing agent; 165 kg of water.
[0083] Example 8
[0084] The composite cement-based concrete, which uses 15% pyrite as a single dopant in sand to replace sand, and 10% wood ash as a single dopant in cement to replace fly ash, comprises the following raw materials:
[0085] 438 kg of cement; 54.7 kg of fly ash; 1182 kg of crushed stone; 430.1 kg of sand; 75.9 kg of fine pyrite sand; 54.7 kg of wood ash; 8.1 kg of water-reducing agent; 165 kg of water.
[0086] Example 9
[0087] Composite cement-based concrete, which uses 15% pyrite as a single dopant in sand to replace sand, and 15% wood ash as a single dopant in cement to replace fly ash, comprises the following raw materials:
[0088] 438 kg of cement; 27.35 kg of fly ash; 1182 kg of crushed stone; 430.1 kg of sand; 75.9 kg of fine pyrite sand; 82.05 kg of wood ash; 8.2 kg of water-reducing agent; 165 kg of water.
[0089] The concrete formulations for Comparative Examples 1-7 and Examples 1-9 are shown in Table 1.
[0090] Table 1
[0091]
[0092]
[0093] To test the performance of concrete, specimens were prepared from the concrete raw materials of Examples 1-9 and Comparative Examples 1-7, respectively:
[0094] (1) Before pouring cement, crushed stone, sand, and pyrite fine sand into the mixer for dry mixing, first vibrate the fly ash and wood ash on the ZH·DG-80 magnetic vibrating table for 1 minute, and then pour them into the mixer.
[0095] (2) Then, pour the cement, crushed stone, sand, and pyrite fine sand into the mixer and dry mix for 60 seconds. Then, add the water-reducing agent to the water, stir evenly, and pour it into the mixer for wet mixing for 180 seconds. The slump of the freshly mixed concrete is about 250 mm and the spread is about 500 mm.
[0096] (3) Specimen preparation and demolding
[0097] After the concrete is mixed, first lay a 20mm long square piece of paper at the bottom of the mold to seal the air pores. Then, evenly apply release agent around the inside of the mold and pour the concrete promptly. Vibrate it on a ZH·DG-80 magnetic vibrating table for one minute, level it, and continue vibrating for 15 seconds. Place it in a standard curing room for curing. Demold the test blocks after 1-2 days of curing.
[0098] Test method: After curing the specimens under standard conditions for 7d, 14d, and 28d, mechanical property tests were conducted using a YAD-2000 microcomputer-controlled electro-hydraulic servo pressure testing machine. According to the "Standard for Test Methods of Mechanical Properties of Ordinary Concrete" (GB / T50081—2002), the loading rates for the compressive strength test were 0.3MPa / s and 0.8MPa / s, and the loading rate for the splitting tensile test was 0.08MPa / s.
[0099] The cubic compressive strength (f) of 16 groups of concrete specimens after 28 days was measured in the experiment. cu ), prism compressive strength (f c ), splitting tensile strength (f s The results of the comparison with the elastic modulus (E) are shown in Table 2. The cubic compressive strength (f) of 16 groups of concrete specimens at 7d, 14d, and 28d were measured in the experiment. cu The results are shown in Table 3. Since the cubic specimens used in the compressive strength test were 100mm × 100mm × 100mm cubes, the actual standard cubic compressive strength (f) is... cu The calculation formula is:
[0100] f cu =0.95f 测 .
[0101] Table 2
[0102]
[0103] Note: The specimen numbering is explained using W5P10 as an example. W5 indicates that 5% wood ash is added to cement and fly ash to replace fly ash, and P10 indicates that 10% pyrite is added to sand to replace sand. Other specimen numbers follow the same pattern.
[0104] Table 3
[0105]
[0106] (4) Performance Analysis
[0107] The water requirement for concrete with added wood ash increases with the amount of wood ash added, where 0% < 5% < 10% < 15%. As the amount of wood ash increases, the slump of the concrete also decreases. This is because the specific surface area of straw ash particles is greater than that of cement, leading to increased water absorption. Simultaneously, it restricts aggregate displacement and cement paste fluidity, thus reducing the slump. Therefore, while keeping the amount of new cement powder particles constant, an appropriate amount of wood ash can be added to prevent excessive addition from causing segregation and bleeding in the cement paste, which would affect the workability of the concrete. The results of the wood ash and water-reducing agent dosages in the experiment are shown in Table 4. Wood ash-pyrite concrete shortens the initial and final setting times of concrete, improves construction efficiency and quality, reduces construction costs, and optimizes construction in low-temperature environments.
[0108] Table 4
[0109]
[0110] (5) Compressive strength analysis
[0111] Concrete incorporating fly ash can improve its crack resistance, impermeability, and resistance to sulfuric acid erosion, as well as its later-stage strength. However, a drawback is its relatively low early-stage strength, and it does not improve the overall durability of the concrete. To address these shortcomings, this paper presents new research progress demonstrating that the protective and passivating effects of straw ash on pyrite can significantly improve the strength of concrete. Figure 1 A three-dimensional bar graph showing the effect of different mixing proportions of wood ash and pyrite on the cubic compressive strength at 7 days. The early strength development of concrete is closely related to parameters such as concrete mix proportion, ambient temperature, and curing time. Figure 1 It can be seen that the compressive strength of the 7-day cubic specimens significantly improved with the increase of wood ash and pyrite. When the content of both wood ash and pyrite was 15%, the compressive strength of the cube reached its maximum, with a 7-day strength of 60.25 MPa, which was 51.27% higher than that of the W0PO group. Figure 2 and Figure 3 A three-dimensional bar chart showing the effect of different mixing ratios of wood ash and pyrite on the compressive strength of cubes. Figure 2 and Figure 3It can be seen that with the increase of wood ash and pyrite, the compressive strength of the 14-day and 28-day cubic specimens still significantly improved. When the content of both wood ash and pyrite was 15%, the cubic compressive strength reached its maximum, with strengths of 63.32 MPa and 72.92 MPa, respectively, representing increases of 24.8% and 31.48%. This is because the properties of pyrite itself, through the passivation effect of wood ash, protect the properties and high strength of pyrite. Pyrite itself is a high-strength mineral with a negative Poisson's ratio, exhibiting high crack resistance and effectively resisting crack propagation and damage. It can reduce stress concentration at the ends of micro-cracks in the concrete matrix and has high energy absorption capacity, absorbing a large amount of energy during concrete loading, thereby inhibiting crack propagation and greatly improving the compressive strength of concrete. Figures 1-3 It can be seen that the bar charts starting from the control group all rise in a step-like manner, indicating that wood ash and pyrite, regardless of their form, will improve the compressive strength of concrete in this experiment. Furthermore, the data shows that wood ash-pyrite concrete can greatly improve the early strength of concrete, making up for the shortcoming of low early strength in fly ash concrete.
[0112] Depend on Figures 4-7 It can be seen that without pyrite, wood ash has only a 3.8% effect on improving the compressive strength of concrete, but with the addition of pyrite, the compressive strength of concrete increases rapidly. Figures 8-11 It can be seen that, without wood ash, pyrite significantly improves the compressive strength of concrete, but not to the maximum extent, at 11.85%. However, with the addition of wood ash, the compressive strength of concrete still increases rapidly. But if we simply add the effects of the two together, 3.8% + 11.85% = 15.65% < 31.48%. Therefore, the simultaneous addition of both wood ash and pyrite creates a "butterfly effect" on the compressive strength of concrete, resulting in a 1+1>2 effect. Figures 4 to 11 It is known that the protection of pyrite by plant ash greatly improves the compressive strength of concrete.
[0113] Figure 12 and Figure 13 The effect of different mixing amounts of wood ash and pyrite on the tensile strength of cubes. Figure 12 As can be seen, the bar chart starting from the control group also shows a stepped upward trend, indicating that the addition of wood ash and pyrite, regardless of their form, increases the compressive strength of concrete within the variables of this experiment. When the content of both wood ash and pyrite is 15%, the cubic compressive strength reaches its maximum of 7.13 MPa, an increase of 31.07%. Figure 3-13It can be seen that the tensile strength of W15P0 has begun to decline. Although it is 2.8% higher than that of W0P0, it is 1% lower than that of W10P0. However, W15P15 is still the highest. Moreover, the increase in pyrite content is most significant at 15% wood ash, reaching 27.55%. This is because the wood ash protects the pyrite, allowing its high crack-breaking properties to be utilized and inhibiting crack formation, thus greatly improving the tensile strength of the concrete.
[0114] (6) Elastic modulus analysis
[0115] Figure 14 The effect of wood ash-pyrite concrete on the modulus of elasticity. Figure 14 It can be seen that the elastic modulus of concrete with only wood ash added did not change significantly, indicating that wood ash alone is not the main material for improving the elastic modulus of concrete, but rather an auxiliary material. The elastic modulus of concrete with both wood ash and pyrite added increased simultaneously, with the W15P15 group showing the highest increase of 9.9%, a considerable result. This indicates that wood ash-pyrite concrete of the same grade has higher strength, stronger load-bearing capacity, better flexural stiffness than ordinary concrete, and is easier to construct.
[0116] (7) Compression-to-tension ratio analysis
[0117] The ratio of cubic compressive strength to splitting tensile strength is one of the indicators for measuring the brittleness of concrete (compression-tensile ratio). Its properties are the same as the tension-compression ratio. The smaller the compression-tensile ratio, the lower the brittleness of the concrete. Figure 15 The effect of different amounts of wood ash-pyrite admixture on the compression-tension ratio of concrete. Figure 15 It can be seen that the compressive strength ratio decreases immediately upon the addition of pyrite. However, as the pyrite content increases, the concrete strength significantly improves, with W5P15 exhibiting the highest compressive-tensile ratio and the highest brittleness. This is because the distribution of wood ash and pyrite fine sand in the concrete is uneven, and the wood ash content is relatively low, failing to fully interact with the pyrite. It merely increases the strength without significantly addressing the brittleness of the concrete. Figure 15 It can also be seen that, overall, the addition of pyrite reduces the brittleness of concrete, enhances its toughness and impact resistance, better absorbs and disperses energy, and reduces structural deformation and damage. While the brittleness increases with higher pyrite content (up to 15%), it remains lower than that without pyrite. Therefore, wood ash-pyrite concrete not only significantly improves concrete strength but also, to some extent, improves its brittleness.
[0118] (8) Elastic strength ratio analysis
[0119] The ratio of elastic modulus to prism compressive strength is one of the indicators for measuring the crack resistance of concrete (elastic-strength ratio). The smaller the elastic-strength ratio, the better the crack resistance of the concrete. Figure 16 The effect of wood ash-pyrite concrete on the elastic strength ratio. (From...) Figure 16 It can be seen that the addition of wood ash-pyrite significantly improves the elastic strength ratio of concrete, with the W15P15 group showing the most significant improvement, reducing it by 19.6% compared to the W0P0 group. While the W5P0, W10P0, and W15P0 groups also show improvement compared to the W0P0 group, the effect is not significant. This indicates that the greater the amount of wood ash and pyrite added, the greater the crack resistance of the concrete. Figure 16 Overall, the higher the content of wood ash, the more fully pyrite plays its role in concrete, and the better the effect on optimizing the crack resistance of concrete.
[0120] (9) Tensile-compressive relationship model prediction
[0121] To further investigate the effects of wood ash and pyrite content on the compressive and tensile strength of concrete. Figure 17 To fit the model of concrete with the same proportions of wood ash and pyrite, the tensile and compressive strength values of groups W0P0, W5P5, W10P10, and W15P15 were fitted. Figure 17 It can be seen that, when using Origin software for curve fitting, the correlation coefficient R0 is... 2 =1, the confidence band and prediction band disappear, the curves almost overlap, and the regression curve fits the experimental curve well, indicating that the model has good applicability. The rate of change of the curve first increases and then decreases, indicating that the tensile-compressive strength relationship between wood ash and pyrite with the same admixture ratio will eventually reach a peak and no longer increase. This also reflects its low brittleness. The fitted regression equation is: y=(719.56136)+(-335.63819)x+(55.04098)x 2 +(-2.90138)x 3 R 2 =1; where: y is the concrete compressive strength / MPa; x is the concrete tensile strength / MPa; R 2 The correlation coefficient represents the goodness of fit. The established regression equation can predict the tensile-compressive strength relationship of concrete with the same admixture ratio of wood ash and pyrite relatively well.
[0122] (10) Analysis of failure morphology of test blocks
[0123] Figure 18 and Figure 19The failure modes of ordinary concrete and wood ash-pyrite concrete specimens in compressive and tensile tests are shown below. In the compressive test of ordinary concrete, no "bang" sound was heard at 7 days. Most of the aggregate in the specimen was not damaged. At failure, the specimen was large and fragmented, with easy surface detachment. The specimen was relatively intact, indicating insufficient mechanical interlocking force between the paste and coarse aggregate, leading to separation of the aggregate from the cement paste, and the aggregate strength was not fully utilized. In contrast, in the 7-day test of wood ash-pyrite concrete (groups W10P10, W10P15, W15P5, W15P10, and W15P15), a relatively soft "bang" sound was heard. Most of the aggregate in the specimen was split in two, indicating more severe damage. At 28 days, the compressive test of ordinary concrete also produced a relatively soft "bang" sound. The specimen was compressed into partially lumpy pieces, with localized aggregate splitting failure, such as... Figure 18 As shown in (a) and (b), multiple groups of wood ash-pyrite concrete samples exhibited a loud "bang" and external collapse of the concrete blocks. The samples showed aggregate splitting failure, severe damage, and numerous fragments at the fracture sites. Figure 19 As shown in (a) and (b).
[0124] In ordinary concrete tensile tests, the concrete specimens all exhibit brittle failure, splitting in two along the cleavage plane. The failure is sudden and severe, without any warning signs beforehand. Figure 18 (c) and Figure 19 As shown in (c).
[0125] The following conclusions can be drawn from the above detection and analysis:
[0126] When wood ash is added alone, the overall compressive strength does not change significantly with the increase of wood ash content, increasing by only 3.8%. Tensile strength initially increases and then decreases. The elastic modulus, compressive-tensile ratio, and elastic-strength ratio also show little change. When pyrite is added alone, the overall compressive strength changes significantly with the increase of pyrite content, increasing by 11.85%. Tensile strength, elastic modulus, compressive-tensile ratio, and elastic-strength ratio show more significant changes compared to the case with wood ash alone. Overall, the mechanical properties of the wood ash-added ...
[0127] With the increase of wood ash and pyrite, the mechanical properties (early strength, cubic compressive strength, tensile strength, modulus of elasticity, compressive-tensile ratio, and elastic-strength ratio) of wood ash-pyrite concrete change significantly. The early strength, cubic compressive strength, tensile strength, and modulus of elasticity increase by 51.27%, 31.48%, 31.07%, and 9.9%, respectively. Through the changes in compressive-tensile ratio and elastic-strength ratio, the toughness, impact resistance, and crack resistance of wood ash-pyrite concrete are significantly improved.
[0128] In terms of compressive strength, the gain ratio of wood ash-pyrite concrete shows a 1+1>2 effect, with wood ash-pyrite concrete (31.48%) > pyrite concrete + wood ash concrete (11.85%+3.8%). Wood ash has a certain passivation effect on pyrite.
[0129] Based on the analysis of the test block failure, the failure effect of the wood ash-pyrite concrete after 7 days was the same as that of the control group after 28 days.
[0130] In conclusion, within a certain range, wood ash-pyrite concrete significantly improves the overall performance of ordinary concrete.
[0131] The technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made in accordance with the technical solutions of the present invention fall within the protection scope of the present invention.
Claims
1. A composite cement-based concrete doped with pyrite and wood ash, characterized in that, The concrete is composed of the following raw materials in parts by weight: 438 parts of cement; 27.35 parts of fly ash; 1182 pieces of crushed stone; 430.1 parts of sand; 75.9 parts of fine pyrite sand; 82.05 parts of corn stalk ash; 8.2 parts water-reducing agent; 165 portions of water; The pyrite fine sand is pyrite fine sand with natural negative Poisson's ratio, with a particle size of 1 mm and a density of 4700 kg / m³. 3 ; The sand is washed medium sand with a fineness modulus of 2.
56.
2. The composite cement-based concrete doped with pyrite and wood ash according to claim 1, characterized in that: The fly ash is Class I, Grade F fly ash, with a density of 2180 kg / m³. 3 Fineness 10.4%.
3. The composite cement-based concrete doped with pyrite and wood ash according to claim 1, characterized in that: The particle size of the crushed stone is 5–20 mm.
4. The composite cement-based concrete doped with pyrite and wood ash according to claim 1, characterized in that: The cement is ordinary Portland cement with a density of 3150 kg / m³. 3 .
5. The composite cement-based concrete doped with pyrite and wood ash according to claim 1, characterized in that: The water-reducing agent is a polycarboxylate water-reducing agent.