A high-ductility high-strength copper-slag-based polyvinyl alcohol fiber reinforced cement-based composite material

Abstract

The application belongs to the technical field of building materials, and particularly relates to a high-ductility high-strength copper residue-based polyvinyl alcohol fiber reinforced cement-based composite material. The composite material is prepared from the following raw materials in parts by weight: cement 450-550 parts, fly ash 550-650 parts, water 350-400 parts, waste copper residue 600-700 parts, polyvinyl alcohol fiber 20-30 parts, and polycarboxylic acid type water reducing agent 1-2 parts. The waste copper residue is used as fine aggregate to replace natural quartz sand by equal volume, and based on the low water absorption, high density and excellent interface bonding performance of the copper residue with the cement matrix, the ultimate tensile strain of the composite material is improved while the strength is maintained, and the self-shrinkage and drying shrinkage of the system are effectively reduced, realizing the synergistic gain of high ductility, low shrinkage and green low carbon.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a high-ductility, high-strength copper slag-based polyvinyl alcohol fiber-reinforced cement-based composite material. Background Technology

[0002] Engineering cement-based composites (ECCs) are widely used in infrastructure construction due to their superior strain hardening and multi-crack characteristics. Polyvinyl alcohol fiber-reinforced cement-based composites (PVA-ECCs), by incorporating appropriate amounts of PVA fibers into the cement matrix, can achieve hundreds of times the ultimate tensile ductility of ordinary concrete and strictly control crack width within 100 micrometers, significantly improving the seismic resistance and durability of the structure. However, traditional PVA-ECCs typically completely eliminate coarse aggregates, resulting in high cementitious material usage, high hydration heat release, and significant shrinkage deformation, easily leading to cracking under non-load conditions. Simultaneously, the surface of PVA fibers is rich in hydrophilic hydroxyl groups, which adsorb large amounts of free water, causing a sharp increase in the viscosity of the freshly mixed mortar, making construction difficult. Furthermore, the mining of natural river sand is increasingly restricted, making the search for its green alternatives an urgent industry need. Copper slag is a large amount of industrial solid waste generated during pyrometallurgical copper smelting; large-scale stockpiling not only occupies land but also poses a risk of heavy metal pollution. If it can be used as a fine aggregate in PVA-ECC, it can both dispose of solid waste and optimize material performance by utilizing its unique physicochemical properties.

[0003] Existing research indicates that copper slag possesses characteristics such as high apparent density, extremely low water absorption, and high hardness. Currently, utilizing copper slag to replace natural quartz sand in the preparation of engineering cement-based composites has become a hot topic in the field of green building materials. However, existing technologies for utilizing copper slag in ECC (Extensive Cemented Carbide) have the following limitations: On the one hand, most studies remain at the stage of partially replacing natural quartz sand with copper slag, with the replacement ratio typically below 100%, failing to completely eliminate dependence on coarse aggregate; on the other hand, a few studies have attempted to use copper slag combined with other auxiliary materials to completely replace quartz sand. While this composite material achieves a certain degree of complete replacement, it increases cost and the complexity of the preparation process. Therefore, there is still a lack of systematic research specifically on the preparation of PVA-ECC using copper slag to completely replace quartz sand, particularly regarding its synergistic regulation mechanism on the tensile ductility and shrinkage properties of the composite material. Summary of the Invention

[0004] This invention provides a high-ductility, high-strength copper slag-based polyvinyl alcohol fiber-reinforced cementitious composite material, aiming to achieve the complete replacement of quartz sand with copper slag in the preparation of PVA-ECC.

[0005] The objective of this invention is achieved through the following technical solution: The high-ductility and high-strength copper slag-based polyvinyl alcohol fiber-reinforced cement-based composite material provided by this invention comprises, by weight, the following raw materials: 450-550 parts cement, 550-650 parts fly ash, 350-400 parts water, 600-700 parts waste copper slag, 20-30 parts polyvinyl alcohol fiber, and 1-2 parts polycarboxylate superplasticizer.

[0006] The raw materials used in the preparation of this invention do not include quartz sand.

[0007] Furthermore, the cement is silicate cement; preferably PO 42.5R grade silicate cement.

[0008] Furthermore, the fly ash is secondary fly ash.

[0009] Furthermore, the waste copper slag has a particle size of 100-200 μm and an apparent density of ≥3000 kg / m³. 3 .

[0010] Furthermore, the polyvinyl alcohol fiber has a tensile breaking strength ≥1600MPa, an elastic modulus ≥35GPa, and an elongation at break ≥6.0%; the density of the polyvinyl alcohol fiber is 1200-1400kg / m³. 3 The polyvinyl alcohol fiber has a length of 10-14 mm and a diameter of 30-50 μm; the volume of the polyvinyl alcohol fiber accounts for 2.0% of the volume of the composite material.

[0011] Furthermore, the polycarboxylate superplasticizer has a water reduction rate of ≥25% and a solid content of ≥5%.

[0012] The present invention also provides a method for preparing the above-mentioned high-ductility and high-strength copper slag-based polyvinyl alcohol fiber-reinforced cementitious composite material, comprising the following steps: S1. Mix the cement, fly ash, and copper slag evenly. S2. Add water and polycarboxylate superplasticizer, and stir to form cement mortar base material; S3. Add the polyvinyl alcohol fiber to the cement mortar substrate and continue stirring until the fiber is uniformly dispersed to obtain the high-ductility, high-strength copper slag-based polyvinyl alcohol fiber-reinforced cement-based composite material.

[0013] The present invention also provides the use of the above-mentioned high ductility and high strength copper slag-based polyvinyl alcohol fiber reinforced cementitious composite material, namely, as a concrete material in various building materials.

[0014] This invention utilizes waste copper slag as fine aggregate to replace natural quartz sand by an equal volume (100%) in the preparation of PVA-ECC, achieving the following significant beneficial effects: 1. Significantly Improved Tensile Ductility and Strength: In this invention, copper slag particles with a diameter of 150 μm achieve good frictional constraint at the fiber-matrix interface within the matrix. Experimental data show that the PVA-ECC prepared using the formulation described in this invention achieves a 28-day ultimate tensile strain of 3.45% and an ultimate tensile strength of 4.22 MPa, representing a nearly 20% improvement in ductility compared to traditional quartz sand-based PVA-ECC (ultimate tensile strain of approximately 2.89%). Microscopic analysis indicates that the appropriate refinement and surface activity of the copper slag promote the optimization of the interfacial transition zone, enabling steady-state slip energy dissipation during tensile testing and inducing dense multi-slit cracking.

[0015] 2. Effective Suppression of Shrinkage and Deformation: Copper slag, as a high-temperature molten water-quenched product, possesses extremely low water absorption (nearly zero) and a dense glassy structure. Compared to the porous and water-absorbing natural quartz sand, the incorporation of copper slag allows more of the mixing water to remain in the slurry as free water, forming ample internal moisture reserves. Experimental results show that the 28-day autogenous shrinkage of the composite material of this invention is 550 μm / m, and the 28-day drying shrinkage is 52 μm / m, far lower than that of traditional quartz sand-based PVA-ECC (autogenous shrinkage 856 μm / m, drying shrinkage 249 μm / m). This internal humidity buffering effect effectively suppresses the development of capillary negative pressure and significantly improves volume stability.

[0016] 3. Achieving Solid Waste Resource Utilization and Green Low-Carbon Development: This invention makes extensive use of waste copper slag (100% replacement rate), reducing the mining of natural river sand and simultaneously disposing of metallurgical solid waste, thus reducing environmental impact. Furthermore, based on the water-reducing effect of copper slag, the amount of polycarboxylate superplasticizer required to maintain the same fluidity is significantly reduced (from 1.51 parts to 1.0 parts), further reducing material costs and carbon emissions. This invention provides a practical and feasible technical path for the high performance and greening of PVA-ECC. Attached Figure Description

[0017] Figure 1 This is a macroscopic morphology diagram of the polyvinyl alcohol fiber of this invention.

[0018] Figure 2 This is a macroscopic morphological diagram of the waste copper slag of this invention.

[0019] Figure 3 This is a microscopic morphology diagram of the copper slag of the present invention.

[0020] Figure 4 This is a gradation distribution diagram of cement, fly ash and glass microspheres in this invention.

[0021] Figure 5 This is a diagram showing the location and dimensions of the specimen in a uniaxial tensile test.

[0022] Figure 6It is the curve showing the relationship between uniaxial tensile stress and strain in a uniaxial tensile test.

[0023] Figure 7 This is a comparison chart of the 28-day shrinkage strain of Embodiment 1 and Comparative Example 1 of the present invention.

[0024] Figure 8 This is a scanning electron microscope (SEM) image (×50, ×500, ×2000, ×5000) of the fracture surface of the tensile specimen in Embodiment 1 of the present invention. Detailed Implementation

[0025] The present invention will now be described in detail with reference to specific embodiments.

[0026] The terms “comprising,” “including,” “having,” “containing,” or any other variations thereof, as used herein, are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0027] When a mass, concentration, temperature, time, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, it should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, the range 1-50 should be understood to include any number, combination of numbers, or subranges selected from 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50, as well as all decimal values ​​between the integers mentioned above, such as 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, and 1.9. Regarding subranges, specifically consider "nested subranges" extending from any endpoint of the range. For example, nested sub-ranges of the exemplary range 1-50 may include 1-10, 1-20, 1-30 and 1-40 in one direction, or 50-40, 50-30, 50-20 and 50-10 in another direction.

[0028] The singular form includes the plural objects of discussion unless the context clearly indicates otherwise. "Optional" or "any one" means that the matter or event described thereafter may or may not occur, and the description includes both the possibility that the event occurs and the possibility that the event does not occur.

[0029] Approximate terms used in the specification and claims to modify quantities indicate that the invention is not limited to that specific quantity, but also includes acceptable modifications close to that quantity that do not alter the relevant essential function. Correspondingly, the use of "about," "approximately," etc., to modify a numerical value means that the invention is not limited to that precise value. In some instances, approximate terms may correspond to the precision of the instrument used to measure the value. In this application's specification and claims, scope definitions can be combined and / or interchanged, unless otherwise stated, these scopes include all subscopes contained therein.

[0030] Furthermore, the indefinite articles “a” and “an” preceding the elements or components of this invention do not impose any limitation on the quantity requirement (i.e., the number of times) of the elements or components. Therefore, “an” or “a” should be interpreted as including one or at least one, and the singular form of an element or component also includes the plural form, unless the quantity clearly refers to the singular form.

[0031] The present invention will be further described below with reference to specific embodiments.

[0032] Examples 1-3 provide a high-ductility, high-strength copper slag-based polyvinyl alcohol fiber-reinforced cementitious composite material, and Comparative Example 1 provides a reinforced cementitious composite material.

[0033] The specific formulations of the examples and comparative examples are shown in Table 1 below: Table 1 1. The polyvinyl alcohol fiber is produced by Kuraray Co., Ltd. (Kuraray Corporation) of Japan, with a density of 1300 kg / m³. 3 It has a length of 12 mm, a diameter of 40 μm, a tensile breaking strength of 1780 MPa, an elastic modulus of 39 GPa, and an elongation at break of 7.0%; its macroscopic morphology is as follows. Figure 1 As shown; from Figure 1 As can be seen, the fiber has good dispersibility and will not tangle into clumps. The amount used is 2.0% of the volume of the composite material.

[0034] 2. The waste copper slag is crushed and screened to a particle size of 150μm, with the following macroscopic morphology. Figure 2-3 As shown, the apparent density is 3560 kg / m³. 3 Its particle size distribution curve is as follows Figure 4 As shown; compared to traditional quartz sand (apparent density 2650 kg / m³) 3 It has higher density and lower water absorption rate.

[0035] 3. The cement is PO 42.5R grade ordinary Portland cement produced by Guangzhou Shijing Cement Company, with an apparent density of 3100 kg / m³.3 The fly ash is classified as Grade II, with an apparent density of 2350 g / m³. 3 Particle size distribution such as Figure 4 As shown.

[0036] 4. The water-reducing agent is a polycarboxylate high-performance water-reducing agent produced by Guangdong Ruian Technology Industry Co., Ltd., with a water reduction rate of 31% and a solid content of 8%.

[0037] 5. The particle size of the quartz sand is 100-360μm, and 471 parts of quartz sand are replaced by 633 parts of copper slag by equal volume.

[0038] The preparation steps of the above embodiments and comparative examples are as follows: S1. Add cement, fly ash and waste copper slag (or quartz sand) into the mixing pot and dry mix to ensure uniform mixing; S2. Mix water and polycarboxylate superplasticizer evenly, then add to a mixing pot and continue stirring to form a cement mortar base material; S3. While stirring, the polyvinyl alcohol fiber is evenly sprinkled into the cement mortar substrate in small amounts multiple times, and stirring is continued until the fiber is fully dispersed, thus obtaining the embodiment.

[0039] Performance tests were conducted on the above embodiments and comparative examples: 1. Tensile ductility test Specimen dimensions for uniaxial tensile testing are as follows: Figure 5 As shown, the specimen consists of a clamping area, a transition area, and a gauge length area. The clamping areas are located at both ends of the specimen and are used to connect the equipment. The gauge length area in the middle is the main body of the specimen, and the transition area between the clamping area and the gauge length area is used to transfer force. The overall dimensions of the tensile specimen are 330 mm long, 60 mm wide, and 13 mm thick. The gauge length area is 80 mm long, 30 mm wide, and 13 mm thick. The uniaxial tensile properties of the cement-based material are obtained by testing the stress-strain relationship along the long side of the gauge length area. The uniaxial tensile testing device uses displacement gauges to fix the support, and one displacement gauge is placed on each side of the specimen to test the tensile displacement along the long side of the gauge length area. At the same time, the testing instrument records the force values ​​during the tensile test. The tensile displacement and tensile force values ​​are converted into tensile strain and tensile stress, respectively, to obtain the uniaxial tensile stress-strain relationship of the gauge length area of ​​the tensile specimen. The tensile test uses a displacement-controlled loading mode with a loading rate of 0.15 mm / min. The results are shown in Table 2 below. Figure 6 As shown: Table 2 Depend on Figure 6As can be seen, the stress-strain curves of Examples 1-3 all exhibit a three-stage development, and the ultimate tensile strain of all three examples exceeds 3%, indicating that polyvinyl alcohol fiber has a good ductility-enhancing effect on high-strength cementitious materials. To further illustrate this enhancement effect, Table 2 records some ductility evaluation indicators of the tensile specimens of Examples 1-3 during the tensile test, such as the ultimate tensile stress (σ). t and ultimate tensile strain (ε) t Furthermore, due to the bridging effect of the fibers, polyvinyl alcohol fibers significantly improve the ultimate tensile stress and ultimate tensile strain of high-strength cement-based materials.

[0040] 2. Shrinkage performance test An integrated shrinkage testing device was used to continuously monitor deformation under sealed conditions (self-shrinkage) and after exposure to the environment (temperature 25±2℃, relative humidity 55±6%) (total shrinkage). The difference was used to calculate the drying shrinkage after 28 days. The results are shown in Table 3 below. Figure 7 As shown: Table 3 The results showed that the autogenous shrinkage (550 μm / m) and drying shrinkage (52 μm / m) of Example 1 were significantly lower than those of Comparative Example 1. This is because the substitution of quartz sand by copper slag resulted in more mixing water remaining in the slurry in a free state, and the low water absorption of copper slag provided the system with a more abundant internal moisture reserve. The abundant internal moisture reserve effectively suppressed fluctuations in internal relative humidity, resulting in a monotonically decreasing trend in both autogenous shrinkage and drying shrinkage.

[0041] 3. Microscopic morphology analysis The tensile fracture surface of Example 1 was observed using a scanning electron microscope (SEM), and the results are as follows: Figure 8 As shown in the image, the 50x magnification reveals that the fibers are well dispersed in the matrix, with numerous fiber pull-out channels and broken fibers present in the cross-section, indicating a high-energy-consuming slippage process. The 500x magnification image shows that the fiber surface is uniformly coated with a dense hydration product (CSH gel), accompanied by obvious longitudinal friction scratches, proving that the copper slag-optimized interface transition zone provides ideal frictional bond strength, preventing both premature fiber breakage and anchoring failure.

[0042] In summary, this invention successfully prepared a PVA-ECC with high ductility (ultimate tensile strain >3%), high tensile strength, and low shrinkage by replacing 100% of quartz sand with 150μm waste copper slag and optimizing the amount of water-reducing agent. This composite material not only achieves high-value utilization of metallurgical solid waste but also significantly improves the mechanical and volumetric stability of traditional ECC, showing broad prospects for engineering applications.

[0043] It is understood that the above specific embodiments are all further illustrations of the present invention and are not intended to limit the scope of protection of the present invention. For those skilled in the art, all other modifications and refinements obtained without creative effort are within the scope of protection of the present invention.

Claims

1. A high-ductility, high-strength copper slag-based polyvinyl alcohol fiber-reinforced cementitious composite material, characterized in that, By weight, the raw materials for preparation include: 450-550 parts cement, 550-650 parts fly ash, 350-400 parts water, 600-700 parts waste copper slag, 20-30 parts polyvinyl alcohol fiber, and 1-2 parts polycarboxylate superplasticizer.

2. The high-ductility, high-strength copper slag-based polyvinyl alcohol fiber-reinforced cementitious composite material according to claim 1, characterized in that, Quartz sand is not included in the raw materials used in the preparation.

3. The high-ductility, high-strength copper slag-based polyvinyl alcohol fiber-reinforced cementitious composite material according to claim 1, characterized in that, The cement is silicate cement.

4. The high-ductility, high-strength copper slag-based polyvinyl alcohol fiber-reinforced cementitious composite material according to claim 1, characterized in that, The fly ash is grade II fly ash.

5. The high-ductility, high-strength copper slag-based polyvinyl alcohol fiber-reinforced cementitious composite material according to claim 1, characterized in that, The particle size of the waste copper slag is 100-200μm.

6. The high-ductility, high-strength copper slag-based polyvinyl alcohol fiber-reinforced cementitious composite material according to claim 1, characterized in that, The polyvinyl alcohol fiber has a tensile breaking strength ≥1600MPa, an elastic modulus ≥35GPa, and an elongation at break ≥6.0%.

7. A method for preparing a high-ductility, high-strength copper slag-based polyvinyl alcohol fiber-reinforced cementitious composite material according to any one of claims 1-6, characterized in that, Includes the following steps: S1. Mix the cement, fly ash, and copper slag evenly. S2. Add water and polycarboxylate superplasticizer, and stir to form cement mortar base material; S3. Add the polyvinyl alcohol fiber to the cement mortar substrate and continue stirring until the fiber is uniformly dispersed to obtain the high-ductility, high-strength copper slag-based polyvinyl alcohol fiber-reinforced cement-based composite material.

8. Use of the high-ductility, high-strength copper slag-based polyvinyl alcohol fiber-reinforced cementitious composite material according to any one of claims 1-6.

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