Plastic waste concrete and preparation method thereof

Abstract

The invention belongs to the technical field of concrete, and particularly relates to plastic waste concrete and a preparation method thereof. The preparation method comprises the following steps: mixing and stirring the cement, the fine aggregate, the coarse aggregate, the additive and the water to obtain a mixture; the fine aggregate comprises plastic waste and river sand; the mixture is compressed and poured, and the plastic waste concrete is obtained. The compactness of the plastic waste (PW) concrete is enhanced through a compression pouring technology, the porosity is reduced, the microstructure of the concrete is densified, the combination of cement and PW is enhanced, the mechanical property of the concrete can be effectively improved, and the compressive strength and the splitting tensile strength are high. The whole preparation process follows a traditional concrete stirring procedure, and no chemical reagent or mineral admixture needs to be added. The invention not only provides a sustainable scheme for solving the problem of river sand shortage, but also deals with the challenge of plastic waste management.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of concrete, and particularly relates to a plastic waste concrete and a preparation method thereof. BACKGROUND

[0002] Concrete is an important material in the field of construction, and is valued for its wide availability, superior performance, and cost-effectiveness. Aggregate (aggregate) is one of the main components of concrete, and the production scale of concrete is huge, and the demand for natural river sand is increasing, therefore, it has become a key priority to find sustainable alternative materials to replace natural river sand in concrete production.

[0003] Plastic has become an indispensable material in modern society, and is widely used in packaging, construction, automobiles, electronics, agriculture and other industries due to its lightweight, economical and multifunctional nature. However, the rapid increase in plastic production has also led to a significant increase in plastic waste (PW). These non-degradable plastic wastes pose a serious challenge to the environment, including pollution of land, air and water bodies. Plastic can pollute the soil, reduce soil fertility, and seep into water bodies, threatening marine ecosystems, as marine organisms ingest harmful plastic debris. Burning or landfilling PW can further worsen the environment by emitting toxic gases and harmful chemicals into the soil and groundwater. Integrating plastic waste into concrete construction materials in an innovative way provides a sustainable alternative to natural resources such as river sand.

[0004] Unlike natural aggregates, PW has a smooth surface and is impermeable to water, which results in a decrease in cohesion at the interface between the cement matrix and the PW. In addition, the stiffness and strength of PW are lower than those of river sand, leading to stress concentration and crack formation within the concrete, further compromising its mechanical properties. Currently, the use of PW as a substitute for river sand in concrete production results in concrete with generally poor mechanical properties, which is a major challenge in using PW as a sustainable alternative to river sand in concrete production. SUMMARY

[0005] Therefore, the present application aims to provide a plastic waste concrete and a preparation method thereof. The plastic waste concrete prepared by the preparation method provided by the present application has good mechanical properties, and solves the problem of poor mechanical properties of concrete after adding PW.

[0006] The present application provides a preparation method of a plastic waste concrete, comprising the following steps: mixing and stirring cement, fine aggregate, coarse aggregate, additive and water to obtain a mixture; the fine aggregate comprises plastic waste and river sand; compressing and pouring the mixture to obtain a plastic waste concrete.

[0007] Preferably, the particle size of the plastic waste is 2-5mm, and the bulk density is 900-1200kg / m 3 ; the material of the plastic waste is polypropylene.

[0008] Preferably, the fineness modulus of the river sand is 2-3, the bulk density is 1600-1800kg / m 3 , and the water absorption rate is 2-4%.

[0009] Preferably, the volume ratio of the plastic waste and the river sand is 0.2-0.4:0.6-0.8.

[0010] Preferably, the coarse aggregate is granite stone, and the particle size of the coarse aggregate is 5-20mm.

[0011] Preferably, the additive is polycarboxylic acid water reducing agent.

[0012] Preferably, the amount of water is such that the water-cement ratio is 0.2-0.4.

[0013] Preferably, per m 3 of the mixture, the following amounts of raw materials are included: cement 510kg, fine aggregate 391-469kg, coarse aggregate 785kg, and additive 2547mL.

[0014] Preferably, the pressure of the compression casting is 10-20MPa.

[0015] The application also provides the plastic waste concrete prepared by the preparation method.

[0016] Compared with the prior art, the application has the following beneficial effects: The application provides a preparation method of plastic waste concrete, which comprises the following steps: mixing and stirring cement, fine aggregate, coarse aggregate, additive and water to obtain a mixture; the fine aggregate comprises plastic waste and river sand; and the mixture is compression cast to obtain plastic waste concrete.

[0017] The application enhances the compactness of the plastic waste (PW) concrete by compression casting technology, reduces the porosity, densifies the microstructure, and enhances the combination of cement and PW, so that the mechanical properties, compressive strength and splitting tensile strength of the concrete can be effectively improved, and the problem of poor mechanical properties of the concrete after adding PW is solved.

[0018] The present invention uses plastic waste as a partial replacement of river sand to enhance the material properties through the compression casting technique. The entire preparation process follows the conventional concrete mixing procedure without the addition of any chemical admixture or mineral admixture, highlighting the application potential of PW in concrete. This not only provides a sustainable solution to the river sand shortage problem but also addresses the challenge of plastic waste management.

[0019] The present invention prepared PW concrete specimens containing 0%, 20%, and 40% (volume replacement rate of river sand) by the compression casting technique, with a target strength of 70 MPa. The results of the study on the axial stress-strain behavior, microstructure, and durability of the compression-cast high-strength PW concrete show that with the increase in PW content (up to 40%), the compressive strength, elastic modulus, and splitting tensile strength of the concrete decrease by 48%, 33%, and 37%, respectively, due to the weakening of the interfacial transition zone (ITZ) and the increase in porosity. The compression casting method significantly enhances the mechanical properties, with the compressive strength of the compression-cast PW concrete increasing by up to 103%, the elastic modulus increasing by up to 53%, and the splitting tensile strength increasing by up to 63% compared to the non-compression-cast PW concrete. In addition, compression casting reduces the porosity of the PW concrete, increases its bulk density, and improves its water resistance. Scanning electron microscope (SEM) analysis shows a denser microstructure and better ITZ quality. The present invention highlights the potential of PW as a viable, sustainable replacement for river sand in concrete, providing a solution for PW management and contributing to environmental sustainability. The compression casting technique enables up to 40% PW replacement without compromising structural performance, making it a promising method for sustainable building practices. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention, and for those skilled in the art, other drawings can also be obtained without creative labor based on these drawings.

[0021] Figure 1 The grading curve of coarse and fine aggregate river sand in the present invention; Figure 2 The actual picture of plastic waste (PW) used in the present invention; Figure 3 The device diagram for preparing compression concrete specimens in the embodiments; Figure 4 The experimental device diagram for evaluating the stress-strain response of the specimens; Figure 5 The results of the failure mode of the concrete specimens; Figure 6 and Figure 7 Effect of PW on the stress-strain behavior of the specimen, wherein Figure 6 is the uncompressed specimen, Figure 7 is the compressed specimen; Figures 8-10 Effect of the compressed casting technique on the stress-strain behavior of the specimen, wherein Figure 8 is M70, Figure 9 is M70-P20, Figure 10 is M70-P40; Figure 11 Comparison results of the stress-strain behavior of the conventional concrete and the compressed casting PW concrete; Figure 12 Comparison results of the compressive strength of the compressed concrete and the uncompressed concrete with different proportions of PW; Figure 13 Comparison results of the elastic modulus of the compressed concrete and the uncompressed concrete with different proportions of PW; Figure 14 Comparison results of the peak strain of the compressed concrete and the uncompressed concrete with different proportions of PW; Figure 15 Comparison results of the ultimate strain of the compressed concrete and the uncompressed concrete with different proportions of PW; Figure 16 Comparison results of the toughness of the compressed concrete and the uncompressed concrete with different proportions of PW; Figure 17 Comparison results of the specific toughness of the compressed concrete and the uncompressed concrete with different proportions of PW; Figure 18 Comparison results of the splitting tensile strength of the compressed concrete and the uncompressed concrete with different proportions of PW; Figure 19 Comparison results of the bulk density of the compressed concrete and the uncompressed concrete with different proportions of PW; Figure 20 Comparison results of the water absorption of the compressed concrete and the uncompressed concrete with different proportions of PW; Figure 21 Comparison chart of the microstructure of M70-P40 and M70-P40-C specimens. DETAILED DESCRIPTION

[0022] The present application provides a preparation method of plastic waste concrete, comprising the following steps: Mixing and stirring cement, fine aggregate, coarse aggregate, additive and water to obtain a mixture; the fine aggregate comprises plastic waste and river sand; Compressively casting the mixture to obtain plastic waste concrete.

[0023] In the present application, the materials and devices used are commercially available in the art, unless otherwise specified.

[0024] The cement, fine aggregate, coarse aggregate, additive and water are mixed and stirred to obtain a mixture.

[0025] In the present application, the cement is preferably Portland cement (OPC, P042.5).

[0026] In the present application, the particle size of the plastic waste (PW) is preferably 2-5 mm, and can be 3 mm in particular. The plastic waste is preferably cylindrical black particles, and the bulk density is preferably 900-1200 kg / m 3 , and can be 1014 kg / m 3 in particular. The material of the plastic waste is preferably polypropylene. The plastic waste is preferably dried before use, and the drying temperature is preferably 60-100℃, and the time is preferably 24 h.

[0027] In the present application, the fineness modulus of the river sand is preferably 2-3, and can be 2.69 in particular. The bulk density is preferably 1600-1800 kg / m 3 , and can be 1729 kg / m 3 in particular. The water absorption is preferably 2-4%, and can be 2.9% in particular. The river sand is preferably dried before use, and the drying temperature is preferably 60-100℃, and the time is preferably 24 h.

[0028] In the present application, the volume ratio of the plastic waste and river sand is preferably 0.2-0.4:0.6-0.8, and can be 0.2:0.8 or 0.4:0.6 in particular.

[0029] In the present application, the coarse aggregate is preferably granite stone, and the maximum particle size of the coarse aggregate is preferably 20 mm, and the particle size range can be 5-20 mm in particular. The coarse aggregate is preferably dried before use, and the drying temperature is preferably 60-100℃, and the time is preferably 24 h.

[0030] In the present application, the additive is preferably a polycarboxylic acid water reducer. The present application does not have special requirements for the source of the polycarboxylic acid water reducer, and the density of the polycarboxylic acid water reducer is preferably 1 g / cm 3 . The dosage of the polycarboxylic acid water reducer is preferably 0.5% by weight of the cement.

[0031] In the present application, the amount of water is preferably such that the water-cement ratio is 0.2-0.4, and can be 0.3 in particular.

[0032] In this invention, per m 3 The mixture meter includes the following raw materials in the following quantities: 510 kg of cement, 391~469 kg of fine aggregate, 785 kg of coarse aggregate, and 2547 mL of admixture; Specifically, it may include: 510 kg of cement, 375 kg of river sand, 55 kg of plastic waste, 785 kg of coarse aggregate, and 2547 mL of admixtures; Alternatively, it may include: 510 kg of cement, 110 kg of river sand, 281 kg of plastic waste, 785 kg of coarse aggregate, and 2547 mL of admixtures.

[0033] The present invention does not have special requirements for the mixing and stirring; methods commonly used by those skilled in the art can be adopted. In an embodiment of the present invention, fine aggregate and coarse aggregate are poured into a mixing pot and stirred for 2-3 minutes, then cement is added and stirred for 2-3 minutes, and finally water and admixtures are added in two batches, each time stirring for 1-1.5 minutes.

[0034] After obtaining the mixture, the present invention compresses and pours the mixture to obtain plastic waste concrete.

[0035] In this invention, the pressure of the compression casting is preferably 10-20 MPa, specifically 15 MPa; the duration of the pressure is preferably 2 minutes. The compression casting is preferably carried out in a steel mold; and the material is preferably vibrated and compacted before compression casting.

[0036] In this invention, the process after compression casting preferably includes curing, wherein the curing temperature is preferably 20°C, the relative humidity is preferably 95%, and the curing time is preferably 28 days.

[0037] The present invention also provides plastic waste concrete obtained by the preparation method described in the above technical solution.

[0038] This invention uses plastic waste (PW) as a sustainable alternative to river sand in concrete, providing a solution to the serious challenges of plastic waste management and the depletion of river sand resources in concrete production.

[0039] To further illustrate the present invention, the following detailed description of the plastic waste concrete and its preparation method provided by the present invention is given in conjunction with the accompanying drawings and embodiments, but these descriptions should not be construed as limiting the scope of protection of the present invention.

[0040] In the embodiments or comparative examples of this invention, the materials used include: Ordinary Portland cement (OPC, PO42.5) and tap water are the main components of the concrete. Coarse aggregate consists of granite gravel with a maximum particle size of 20mm, supplied by a local supplier in Shenzhen; its characteristics are shown in Table 1. River sand is sourced from Shenzhen, China, with a fineness modulus of 2.69 and a bulk density of 1729 kg / m³. 3 The characteristics are shown in Table 2. The particle size distribution curves of the coarse aggregate and river sand conform to ASTM C33:2016 standard, such as... Figure 1 As shown. The plastic waste (PW) comes from a plastic recycling plant in Dongguan, China. The PW is primarily made from recycled polypropylene, is cylindrical, black in color, and has a uniform particle size of 3mm (see...). Figure 2 Its bulk density is 1014 kg / m³. 3 It is 41% lower than that of river sand, see Table 2.

[0041] Table 1 Characteristics of coarse aggregate

[0042] Table 2 Properties of fine aggregates (river sand and PW)

[0043] Examples 1-2 and Comparative Examples 1-4 The specifications of the concrete specimens are detailed in Table 3, where the target compressive strength of the compression-cast concrete is 70 MPa. Table 3 lists three different volume percentages of PW replacement (0%, 20%, and 40%). Specimen designations in Table 3 include the target strength, the percentage of PW replacement volume, and the compression casting method. For example, M70-P40-C indicates a compression-cast concrete specimen with a target strength of 70 MPa, where 40% of the river sand volume is replaced by PW.

[0044] Table 4 details the concrete mix proportions. To achieve the target compressive strength of 70 MPa, a water-cement ratio (w / c) of 0.3 was used, and a chemical admixture (polycarboxylate superplasticizer, density 1 g / cm³) was employed. 3 The dosage of PW was 0.5% of the cement weight. PW replaced river sand by volume, with volume replacement rates of 20% and 40%, respectively.

[0045] Prior to mixing, all aggregates were oven-dried for 24 hours to ensure consistent moisture content. Concrete was prepared using a twin-shaft concrete mixer according to the ASTM C192:2016 standard procedure. Subsequently, 100 mm × 200 mm cylindrical specimens of each mixture were cast, including both compressed and uncompressed specimens.

[0046] The traditional method for preparing concrete is as follows: First, pour fine aggregate and granite into a mixing pot and mix for 2 minutes. Then, add cement and mix for 2 minutes. Finally, add water and admixtures in two batches, mixing for 1 minute each time to obtain a mixture. Pour the mixture into a conventional mold, vibrate it to make it compact, and then remove the mold after 24 hours. Then, place it in a standard curing room and cure it for 28 days.

[0047] The method for preparing compression cast concrete is as follows: First, pour fine aggregate and granite into a mixing pot and mix for 2 minutes. Then, add cement and mix for 2 minutes. Finally, add water and admixtures in two batches, mixing for 1 minute each time to obtain a mixture. Pour the mixture into a steel mold, vibrate to compact it, and then perform compression casting. After 24 hours, remove the mold and place it in a standard curing room for 28 days.

[0048] The density of traditional concrete is approximately 2200~2400 kg / m³. 3 The density of compressed concrete is approximately 2500~2800 kg / m³. 3 .

[0049] Table 3 Detailed information on concrete samples

[0050] Table 4 Concrete Mix Proportion Specifications

[0051] Note: The admixtures in Table 1 are polycarboxylate superplasticizers, and the mix proportions for compressed concrete are the mix proportions before compression.

[0052] Preparation of compression-cast concrete samples: Freshly mixed concrete was placed in a specially designed mold capable of withstanding high-pressure loads. After filling the mold, a 100-ton capacity hydraulic jack was used to apply a pressure of 15 MPa to the concrete, which was maintained for 2 minutes. The apparatus for the compression casting process is as follows: Figure 3 As shown, it includes a hydraulic jack, a mold, a pressure sensor, and a pressure value display.

[0053] After pouring, the compressed concrete specimens were placed in molds for 24 hours, following the same procedure as the uncompressed specimens. Afterward, the molds were removed, and all specimens (both compressed and uncompressed) were cured for 28 days at 20°C and 95% relative humidity.

[0054] To evaluate the stress-strain behavior of uncompressed and compressed concrete specimens, this invention employs a displacement-controlled mode, performing uniaxial compression tests at a loading rate of 0.3 mm / min. A data acquisition system records the load-bearing capacity of the specimens. Axial displacement is measured using four linear variable displacement sensors (LVDTs) mounted on an aluminum frame in the middle of the specimen. Figure 4Experimental setups for analyzing stress-strain behavior were demonstrated, including an aluminum frame, a pressure sensor, and a linear variable displacement sensor.

[0055] Splitting tensile strength was tested according to ASTM C496:2017. Three specimens were selected for each test configuration, and the average value was reported to ensure the reliability of the results. For further analysis of material properties, the water absorption and bulk density after immersion were measured according to ASTM C642:2013. Porosity and microstructure were investigated using the mercury intrusion porosity assay (MIP) and scanning electron microscopy (SEM).

[0056] Test case 1. Damage Mode Analysis Figure 5 The failure modes of all tested concrete specimens are presented. No obvious cracks appeared in any specimen before reaching the peak load. For the uncompressed specimens, surface cracks began to appear after reaching the peak load and gradually expanded with further loading. These specimens also exhibited surface spalling before complete failure (when the peak load decreased to approximately 85%). Conversely, the compressed specimens developed surface cracks abruptly upon reaching the peak load, leading to sudden and brittle failure. The brittle behavior of the compressed cast specimens was more pronounced compared to the uncompressed specimens using the same concrete.

[0057] Replacing river sand with polysilicon (PW) significantly affected the failure modes of concrete specimens, leading to an increase in the number of cracks but a decrease in their size. Furthermore, the increased PW content reduced brittle failure, both under compressive and uncompressive conditions.

[0058] 2. Stress-strain behavior Figure 6 and Figure 7 The effect of PW on the stress-strain behavior of compressed and uncompressed specimens is shown. When PW replaces river sand, the stress-strain curves of the uncompressed concrete specimens show a lower stress-strain relationship. Figure 6 As shown, both the initial slope (i.e., elastic modulus) and peak stress decrease with increasing PW content. Furthermore, the descending portion of the stress-strain curve becomes less steep with increasing PW content, indicating reduced brittleness. This phenomenon is attributed to a weaker interfacial transition zone (ITZ) between the cement paste and PW, resulting in poorer bond strength compared to river sand. The failure surface shifts from the brittle cement paste to the weaker ITZ, further exacerbating this problem.

[0059] For compression-cast specimens, such as Figure 7As shown, when PW is used instead of river sand, the initial slope, peak stress, and descent slope of the stress-strain curve are all reduced. However, these reductions are not as significant as those in the uncompressed specimens. This suggests that compression casting techniques may mitigate the adverse effects of PW on the stress-strain behavior of concrete.

[0060] Figures 8-10 The effect of compression casting on the stress-strain behavior of concrete specimens was demonstrated. Compared to uncompressed specimens, compressed specimens exhibited higher stress-strain curves. The stress-strain curves of compressed-cast specimens showed a steeper upward slope and higher peak stress values, indicating improved stiffness and strength. Similarly, the downward slope of the stress-strain curves of compressed-cast specimens was also steeper than that of uncompressed specimens, reflecting more brittle failure characteristics. Notably, the effects of compression casting were similar for specimens containing polywheat ore (PW) and those using river sand, suggesting that compression casting is effective in improving the mechanical properties of PW-containing concrete. This indicates that the compression casting method can promote the widespread application of PW in concrete production.

[0061] Figure 11 The stress-strain behavior of conventional concrete specimens (M70) and compression-cast PW concrete specimens (M70-P40-C) was compared. The stress-strain curves of the M70 specimens were very close to those of the M70-P40-C specimens, indicating that compression casting effectively alleviates the performance problems when using PW and supports the recycling of PW as a fine aggregate in concrete production.

[0062] 3. Compressive strength Figure 12 The compressive strength of uncompressed and compressed concrete with different PW contents is shown. For the uncompressed samples, the compressive strength of all concretes decreased significantly with increasing PW content. For example, compared with uncompressed M70 concrete (45.66 MPa), the compressive strength of uncompressed M70-P20 (33.31 MPa) and M70-P40 (23.61 MPa) concrete decreased by 27% and 48%, respectively. These reductions are mainly attributed to the smooth, impermeable surface of PW, which has lower resistance and disrupts the cohesion between the cement matrix and aggregates.

[0063] For compression-cast specimens, the compressive strength decreased with increasing PW content, but this trend was less pronounced than in uncompressed concrete. For example, compared to the compression-cast M70 specimen (70.61 MPa), the compressive strength of the compression-cast M70-P20 (51.43 MPa) and M70-P40 (47.90 MPa) specimens decreased by 27% and 32%, respectively; these decreases were attributed to the same factors mentioned above. However, compared to the compression-cast and uncompressed M70 specimens, the compressive strength of the compression-cast and uncompressed M70-P40 specimens decreased by 32% and 48%, respectively, with the decrease in compression-cast being less significant. This indicates that compression casting has a significant effect in mitigating the negative impact of PW in concrete. Compression casting improves the pore structure, thereby enhancing mechanical properties.

[0064] Figure 12 This study demonstrates that compression casting technology significantly improves compressive strength. After compression casting, the compressive strength of M70, M70-P20, and M70-P40 samples increased by 55%, 54%, and 103%, respectively. The concrete with higher PW content, such as M70-P40, showed the most significant improvement. This is mainly because compression casting has a greater impact on low-strength concrete (such as uncompressed M70-P40), which typically has higher porosity.

[0065] Interestingly, the compressive strength of the compressed-cast M70-P40 specimens was slightly higher than that of the uncompressed M70 specimens. This finding suggests that compression casting technology provides a viable solution for replacing river sand with up to 40% PW in concrete production, promoting sustainable practices without significantly impacting performance.

[0066] 4. Elastic modulus Figure 13 The modulus of elasticity of uncompressed and compressed cast concrete containing different proportions of polyunsaturated concrete (PW) was demonstrated. In the uncompressed specimens, the modulus of elasticity decreased significantly with increasing PW proportion; for example, the modulus of elasticity of M70-P20 (26.08 GPa) and M70-P40 (21.74 GPa) specimens were 19% and 33% lower, respectively, than that of uncompressed M70 concrete (32.28 GPa). A similar but less pronounced trend was observed in the compressed specimens, with the modulus of elasticity of M70-P20 (34.57 GPa) and M70-P40 (33.18 GPa) specimens being 14% and 18% lower, respectively, than that of the compressed M70 specimen (40.37 GPa).

[0067] These reductions are primarily attributed to the smoothness and hydrophobicity of the PW surface, which weakens the cohesion and bond strength between the cement matrix and the aggregate. Other factors include the formation of stress concentration zones, weaknesses in the ITZ (interfacial transition zone), increased air porosity, the low elastic modulus of PW, poor gradation, porosity, and differences in particle size distribution compared to river sand.

[0068] Compared to compressed and uncompressed M70 specimens, the elastic modulus of the compressed and uncompressed M70-P20 specimens decreased by 14% and 19%, respectively. Similarly, the elastic modulus of the compressed and uncompressed M70-P40 specimens decreased by 18% and 33%, respectively. These results demonstrate that compression casting technology is significantly effective in mitigating the negative effects of water-aggregate interactions (PW) in concrete. By applying pressure, compression casting can reduce porosity, enhance the bonding force between aggregates, and expel excess moisture and air, thereby improving the mechanical properties of the material.

[0069] The trend of incorporating PW into concrete has a similar effect on the modulus of elasticity as it does on compressive strength. Figure 13 This demonstrates that compression casting significantly improved the modulus of elasticity. The modulus of elasticity of M70, M70-P20, and M70-P40 samples increased by 25%, 33%, and 53%, respectively, after compression. Concrete with higher PW content, such as M70-P40, showed the most significant improvement. This improvement is mainly attributed to the greater effect of compression casting on low-strength concrete (such as uncompressed M70-P40), which typically has higher porosity.

[0070] Interestingly, the elastic modulus of the compressed M70-P40 specimen was slightly higher than that of the uncompressed M70 specimen. This indicates that compression casting technology can effectively use up to 40% PW as a substitute for river sand in concrete production, supporting sustainable practices without significantly affecting performance.

[0071] 5. Peak strain Figure 14Peak strains of uncompressed and compressed concrete with different PW contents are shown. In the uncompressed specimens, the peak strain increases significantly with increasing PW content. For example, the peak strains of the M70-P20 (0.00221) and M70-P40 (0.00270) specimens are 18% and 44% higher than those of the uncompressed M70 (0.00188) specimen, respectively. The increase in peak strain after adding PW is attributed to the enhanced deformation capacity and reduced concrete strength. This phenomenon stems from the compressibility of PW, weakened aggregate-mortar bond strength, and altered pore structure. In the compressed specimens, the peak strains of the M70-P20 (0.00190) and M70-P40 (0.00193) specimens are 4% and 6% higher than those of the compacted M70 (0.00182) specimen, respectively; this trend is similar but less pronounced.

[0072] Compared to compressed-cast and uncompressed-cast M70 specimens, the peak strain of compressed-cast and uncompressed-cast M70-P20 increased by 4% and 18%, respectively, while that of M70-P40 increased by 6% and 44%, respectively. These results demonstrate that compression casting has significant advantages in mitigating the negative impacts of plastic waste (PW) in concrete. Compression casting reduces porosity, enhances inter-aggregate interactions, and restricts deformation capacity, thereby reducing peak strain.

[0073] Figure 14 The results demonstrate a significant reduction in peak strain achieved through compression casting. The peak strain of the M70, M70-P20, and M70-P40 specimens decreased by 3%, 14%, and 29%, respectively, after compression, with the concrete with higher PW content, such as M70-P40, showing the most significant strain reduction.

[0074] It is noteworthy that the peak strain of the compacted M70-P40 specimen was almost the same as that of the uncompacted M70 specimen, indicating that the compression casting technique can effectively use up to 40% PW as a substitute for river sand in concrete production, supporting sustainable practices without significantly affecting performance.

[0075] 6. Ultimate strain Figure 15The ultimate strain of uncompressed and compressed concrete with different PW contents is shown. In the uncompressed samples, the ultimate strain increases significantly with increasing PW content. For example, the ultimate strains of the M70-P20 (0.00294) and M70-P40 (0.00433) specimens are 14% and 69% higher than those of the uncompressed M70 (0.00257) specimen, respectively. This is likely due to the enhanced deformation capacity and reduced concrete strength. In the compressed samples, the ultimate strains of the M70-P20 (0.00241) and M70-P40 (0.00260) specimens are 9% and 17% higher than those of the compressed M70 (0.00221) specimen, respectively. While the trend is similar, it is less pronounced.

[0076] Compared with the compressed and uncompressed cast M70 specimens, the ultimate strain of the compressed and uncompressed cast M70-P20 increased by 9% and 14%, respectively, while that of the M70-P40 increased by 17% and 69%, respectively. These data indicate that the compression casting technology plays a positive role in mitigating the adverse effects of PW (plastic waste) in concrete.

[0077] Figure 15 The results demonstrate a significant reduction in final strain achieved through compression casting. The ultimate strain of the M70, M70-P20, and M70-P40 specimens decreased by 14%, 18%, and 40%, respectively, after compaction, with the concrete with higher PW content, such as M70-P40, showing the most significant strain reduction.

[0078] Notably, the ultimate strength of the compressed M70-P40 specimens was almost identical to that of the uncompressed M70 specimens. This indicates that compression casting technology can effectively utilize up to 40% PW as a substitute for river sand in concrete production, supporting sustainable practices without significantly impacting performance.

[0079] 7. Toughness Figure 16 The toughness of uncompressed and compressed concrete with different PW contents was demonstrated, determined by calculating the area under the stress-strain curves at the ultimate strain. In the uncompressed specimens, toughness decreased slightly with increasing PW content. For example, compared to the uncompressed M70 (0.0809 MPa) specimen, the toughness of the M70-P20 (0.0723 MPa) and M70-P40 (0.0754 MPa) specimens decreased by 11% and 7%, respectively. A similar trend was observed in the compressed specimens, with the toughness of the M70-P20 (0.0816 MPa) and M70-P40 (0.0791 MPa) specimens decreasing by 15% and 17%, respectively, compared to the compressed M70 (0.0955 MPa) specimen. This decrease in toughness is attributed to the reduction in compressive strength due to the increased PW content.

[0080] Compared with the compressed and uncompressed M70 samples, the toughness of the compressed and uncompressed M70-P20 decreased by 15% and 11%, respectively, while the toughness of the M70-P40 decreased by 17% and 7%, respectively. Figure 16 The results also showed that the toughness was significantly improved through compression casting technology. Specifically, the toughness of M70, M70-P20 and M70-P40 increased by 18%, 13% and 5% respectively, mainly due to the enhanced compressive strength.

[0081] It is noteworthy that the toughness of the compressed M70-P40 specimens was almost equivalent to that of the uncompressed M70 specimens. This indicates that, through compression casting technology, up to 40% of PW can be used to replace river sand in concrete production, thereby promoting sustainable development without significantly affecting performance.

[0082] 8. Comparison of toughness Figure 17 The specific toughness of uncompressed and compressed concrete with different PW contents is shown, which was determined by calculating the compressive strength. In the uncompressed specimens, the specific toughness increased significantly with increasing PW content. For example, the specific toughness of the M70-P20 (0.217%) and M70-P40 (0.317%) specimens was 22% and 78% higher than that of the uncompressed M70 (0.177%) specimen, respectively. A similar but less significant trend was observed in the compressed specimens, with the specific toughness of the M70-P20 (0.158%) and M70-P40 (0.165%) specimens being 17% and 22% higher than that of the compacted M70 (0.135%) specimen, respectively. This increase in specific toughness with increasing PW content can likely be attributed to enhanced deformation capacity.

[0083] Compared with compressed and uncompressed M70 samples, the specific toughness of compressed and uncompressed M70-P20 was improved by 17% and 22%, respectively. Similarly, the improvements for compressed and uncompressed M70-P40 were 22% and 78%, respectively. These results demonstrate that compression casting technology has significant advantages in mitigating the effects of polyunsaturated concrete (PW) in concrete.

[0084] Figure 17 The study also demonstrated a significant reduction in specific toughness achieved through compression casting. The specific toughness of the M70, M70-P20, and M70-P40 samples decreased by 24%, 27%, and 48%, respectively. After compression, the toughness reduction was most pronounced, especially in concretes with higher PW content, such as M70-P40. This decrease in toughness is primarily due to the greater impact of compression on low-strength concretes, such as uncompressed M70-P40.

[0085] Interestingly, the toughness of the compressed M70-P40 specimens was very close to that of the uncompressed M70 specimens. This indicates that compression casting technology can effectively use up to 40% PW as a substitute for river sand in concrete production, supporting sustainable practices without significantly affecting performance.

[0086] 9. Splitting tensile strength Figure 18 The splitting tensile strength of uncompressed and compressed concrete with different proportions of polysiloxane (PW) was demonstrated. For the uncompressed samples, the splitting tensile strength of all concretes decreased significantly with increasing PW content. For example, the splitting tensile strength of uncompressed M70-P20 (3.4 MPa) and M70-P40 (2.66 MPa) concrete decreased by 20% and 37% respectively compared to uncompressed M70 (4.23 MPa) concrete. These decreases were mainly attributed to several factors: the smooth and hydrophobic surface of PW, weak bond between cement matrix and aggregate, the presence of stress concentration zones, the fragility of the ITZ (interfacial transition zone), increased air porosity, low elastic modulus of PW, poor gradation, high porosity, and differences in particle size distribution compared to river sand. The effect of PW on splitting tensile strength followed a similar pattern to its effect on compressive strength.

[0087] For compression specimens, the splitting tensile strength decreased with increasing PW content, although this decrease was less pronounced than in uncompressed concrete. Specifically, the splitting tensile strength of compressed M70-P20 (4.5 MPa) and M70-P40 (4.33 MPa) specimens decreased by 9% and 12%, respectively, compared to the compressed M70 (4.94 MPa) specimen. The main reasons are consistent with those mentioned earlier. However, when comparing compressed and uncompressed specimens of the same concrete, the decrease in strength of the compressed samples was significantly smaller, i.e., 9% for M70-P20 compared to 20% for uncompressed, and 12% for M70-P40 compared to 37% for uncompressed. This indicates that compression casting is very effective in mitigating the negative impact of PW in concrete. The compression casting process can refine the pore structure, ultimately improving the mechanical properties of the material.

[0088] like Figure 18 As shown, compression casting significantly improved the splitting tensile strength. The strengths of M70, M70-P20, and M70-P40 samples increased by 17%, 32%, and 63%, respectively, all of which occurred after compaction. Notably, the improvement was most pronounced in high PW content concrete, especially in M70-P40. This indicates that for weaker and more porous concretes, such as uncompressed M70-P40, compression casting is more effective.

[0089] Interestingly, the tensile strength of compressed M70-P40 was slightly higher than that of uncompressed M70, indicating that compression casting technology can effectively utilize up to 40% PW as a substitute for river sand in concrete. This not only demonstrates the technology's potential to improve the sustainability of concrete production but also maintains good mechanical properties.

[0090] 10. Bulk density Figure 19 The bulk density of uncompressed and compressed concrete containing different proportions of PW is shown. For the uncompressed samples, the bulk density decreases significantly with increasing PW content. For example, compared with uncompressed M70 (2.59 g / cm³), the bulk density decreases significantly. 3 Compared to the uncompressed M70-P20 sample (2.46 g / cm³), 3 ) and M70-P40 (2.38g / cm 3 The bulk density of the samples decreased by 5% and 8%, respectively. This reduction was mainly due to the lower bulk density of PW compared to river sand, as shown in Table 2. Furthermore, the weaker bond between the cement matrix and aggregate led to increased porosity and air voids, further reducing the bulk density.

[0091] For the compressed sample, the bulk density showed a similar decreasing trend with increasing PW content. Specifically, compared to the compressed M70 (2.77 g / cm³), the bulk density decreased. 3 Compared to the sample, the compressed M70-P20 (2.57 g / cm³) 3 ) and M70-P40 (2.49g / cm 3 The bulk density of the samples decreased by 7% and 10%, respectively. The main reasons for this reduction are consistent with those mentioned earlier. Figure 19 As shown, by reducing voids and removing excess moisture, compression casting significantly increased the bulk density, resulting in a denser structure. Compared to the uncompressed samples, the bulk density of the compressed M70, M70-P20, and M70-P40 samples increased by 7%, 4%, and 4%, respectively.

[0092] Interestingly, the bulk density of the compressed M70-P40 specimen was only slightly lower than that of the uncompressed M70 specimen, indicating that up to 40% of plastic waste (PW) can be used as a substitute for river sand through compression casting technology, while maintaining the performance of concrete. This highlights the potential of compression casting in improving the sustainability of concrete production.

[0093] 11. Water absorption rate Figure 20The water absorption behavior of uncompressed and compressed concrete with different PW contents was demonstrated. In the uncompressed samples, the water absorption rate increased accordingly with increasing PW content. For example, compared with the uncompressed M70 (3.25%) sample, the water absorption rates of the uncompressed M70-P20 (4.96%) and M70-P40 (6.96%) samples increased by 53% and 114%, respectively. This significant increase in water absorption rate is mainly due to the increase in porosity and air voids, which is attributed to the weakening of the bonding force between the cement matrix and aggregate.

[0094] The compressed samples also showed a similar trend; water absorption increased with increasing PW content, but the increase was not as significant as that of the uncompressed samples. For the compressed M70-P20 (3.56%) and M70-P40 (3.90%), their water absorption increased by 59% and 74%, respectively, compared to the compressed M70 sample (2.23%). Although high porosity and weak bonding were the main reasons, this effect was mitigated by the densification effect of compression casting. For example, the water absorption of compressed M70-P40 increased by 74%, while that of uncompressed M70-P40 increased by 114%, indicating that compression casting helps to mitigate the negative impact of PW in concrete.

[0095] like Figure 20 As shown, compression casting significantly reduces the water absorption rate of the materials. Through compression casting, the water absorption rates of M70, M70-P20, and M70-P40 decreased by 31%, 28%, and 44%, respectively. This process effectively removes excess moisture and reduces porosity, resulting in a denser microstructure. The largest reduction was observed in concretes with higher PW content, such as M70-P40, indicating that compression casting has a greater impact on porous and weaker concretes.

[0096] Interestingly, the water absorption rate of compressed M70-P40 was almost the same as that of uncompressed M70. This finding suggests that compressed casting can facilitate the effective use of up to 40% PW as a substitute for river sand in concrete, supporting more sustainable concrete production without compromising performance.

[0097] 12. Porosity Table 5 shows the porosity values ​​of samples M70, M70-P40, and M70-P40-C. Replacing river sand with PW significantly increased porosity. For example, the porosity of M70-P40 was 69% higher than that of M70, primarily due to the weaker bond between the cement matrix and aggregate. In contrast, compression casting significantly reduced the porosity of PW concrete. For instance, the porosity of sample M70-P40-C was 45% lower than that of uncompressed M70-P40. Furthermore, the porosity of M70-P40-C was slightly lower than that of M70, indicating that their performance was comparable. This highlights the effectiveness of compression casting technology in increasing the utilization rate of PW in concrete production while maintaining performance.

[0098] Table 5 Porosity of uncompressed and compressed specimens

[0099] 13. Microstructure Figure 21 Scanning electron microscope (SEM) images of specimens M70-P40 (left) and M70-P40-C (right) reveal significant differences in their microstructures. Both specimens have smooth surfaces. In M70-P40, the interfacial transition zone (ITZ) between the cement matrix and the cementitious matrix (PW) is weak, resulting in poor adhesion. In contrast, specimen M70-P40-C exhibits a significantly improved ITZ and stronger adhesion to the cement matrix.

[0100] Furthermore, the M70-P40 specimen exhibited a weak cement paste structure composed of pores and microcracks. In contrast, the M70-P40-C specimen displayed a denser microstructure with significantly reduced pores and microcracks, demonstrating the effectiveness of the compression casting technique. This technique not only reduces porosity but also optimizes the microstructure. These observations further demonstrate the potential of compression casting to improve the performance of PW concrete while supporting its sustainable recycling without compromising quality.

[0101] This invention utilizes polysilicon (PW) as a sustainable alternative to river sand in concrete, aiming to address challenges such as PW management, river sand resource depletion, and environmental sustainability. The structural performance of concrete with different PW contents (0%, 20%, and 40%) was studied and evaluated using compression casting technology, with a target strength of 70 MPa. The results show that PW concrete exhibits significant potential in structural applications, as detailed below: 1) The addition of polyvinyl chloride (PW) significantly affects the stress-strain behavior of concrete, leading to a decrease in elastic modulus, peak stress, and brittleness due to reduced ITZ strength. However, these effects can be mitigated by employing compression casting techniques, thereby improving the stiffness and strength of the concrete and ensuring its performance is comparable to that of conventional concrete.

[0102] 2) With increasing PW content, the compressive strength, elastic modulus, and splitting tensile strength of the uncompressed specimens decreased by 48%, 33%, and 37%, respectively, mainly due to weakened ITZ bond strength and increased porosity. However, compression casting technology effectively mitigated these performance degradations, increasing compressive strength by 103%, elastic modulus by 53%, and splitting tensile strength by 63% compared to the uncompressed specimens. Notably, compacted PW concrete containing 40% PW content outperformed uncompressed conventional concrete in mechanical properties, demonstrating that compression casting technology can achieve up to 40% PW replacement while maintaining structural performance.

[0103] 3) PW content and compression significantly affect strain behavior and specific toughness. In uncompressed specimens, peak strain and ultimate strain increased by 44% and 69%, respectively, with increasing PW content, reflecting enhanced deformation capacity and weakened ITZ bond. Similarly, specific toughness increased by up to 78% with increasing PW content. Compression casting mitigated these effects, reducing peak strain by 29%, ultimate strain by 40%, and specific toughness by 48%. Notably, compressible concrete containing 40% PW exhibited strain characteristics and specific toughness comparable to conventional uncompressible concrete, demonstrating the effectiveness of compression casting technology in promoting the sustainable use of PW while maintaining structural integrity.

[0104] 4) PW content and compression significantly affect aggregate bulk density, water absorption, and porosity. In uncompressed samples, due to increased porosity and weakened bonding between the cement matrix and aggregate, aggregate bulk density can decrease by up to 8%, while water absorption can increase by 114%. Through compression technology, concrete containing 40% PW can increase aggregate bulk density by 4%, reduce water absorption by 44%, and reduce porosity by 45%, resulting in a denser structure and improved performance. Scanning electron microscopy (SEM) analysis supports these findings, showing that uncompressed samples have weaker interfacial strength (ITZ) and poorer bonding, while compressed samples show significantly enhanced interfacial strength, stronger bonding, and a denser microstructure. This indicates that compression casting technology can significantly improve the sustainability and durability of concrete containing up to 40% PW without sacrificing quality.

[0105] This invention demonstrates the potential of polysilicon (PW) as a sustainable alternative to river sand in concrete. Although increased PW content leads to a decline in mechanical properties, these effects can be significantly mitigated through compression casting techniques, achieving up to 40% PW replacement without compromising performance. Compression-cast PW concrete not only maintains durability and strength but also provides a promising solution for plastic waste management and river sand depletion. These findings support the incorporation of PW into concrete, advance sustainable building practices, and promote environmental sustainability through the utilization of recycled plastic waste materials.

[0106] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, not all embodiments. People can obtain other embodiments based on the present invention without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing plastic waste concrete, characterized in that, Includes the following steps: Cement, fine aggregate, coarse aggregate, additives, and water are mixed and stirred to obtain a mixture; the fine aggregate includes plastic waste and river sand. The mixture is compressed and poured to obtain plastic waste concrete.

2. The preparation method according to claim 1, characterized in that, The plastic waste has a particle size of 2-5 mm and a bulk density of 900-1200 kg / m³. 3 The plastic waste is made of polypropylene.

3. The preparation method according to claim 1, characterized in that, The fineness modulus of the river sand is 2-3, and the bulk density is 1600-1800 kg / m³. 3 The water absorption rate is 2-4%.

4. The preparation method according to claim 1, characterized in that, The volume ratio of the plastic waste to the river sand is 0.2~0.4:0.6~0.

8.

5. The preparation method according to claim 1, characterized in that, The coarse aggregate is granite gravel with a particle size of 5-20 mm.

6. The preparation method according to claim 1, characterized in that, The additive is a polycarboxylate superplasticizer.

7. The preparation method according to claim 1, characterized in that, The amount of water used is such that the water-cement ratio is 0.2 to 0.

4.

8. The preparation method according to claim 1 or 7, characterized in that, per m 3 The mixture meter includes the following raw materials in the following quantities: 510 kg of cement, 391~469 kg of fine aggregate, 785 kg of coarse aggregate, and 2547 mL of admixture.

9. The preparation method according to claim 1, characterized in that, The pressure for compression casting is 10~20MPa.

10. Plastic waste concrete obtained by the preparation method according to any one of claims 1 to 9.

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