Rubber-plastic-glass paving brick

Abstract

The invention provides an environment-friendly paving brick doped with a large amount of recycled waste. Recycled materials are incorporated into the paving brick through various physical and / or chemical treatments, the paving brick shows excellent mechanical strength and durability, ensuring use safety and long-term use ability for pedestrians. By mixing the recycled waste tire rubber, the recycled plastic and the recycled glass into the formula, the paving brick disclosed by the invention still can reach mechanical strength sufficient to load pedestrians. Therefore, the environment-friendly paving brick has huge potential in the aspects of large-scale production and application. Therefore, the invention provides an innovative solution, which not only can meet the increasing waste recovery, but also can meet the increase of the use requirements of the paving brick.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS:

[0001] This application claims priority to U.S. Provisional Patent Application Serial No. 63 / 602,682 filed on November 27, 2023, and the disclosure of the U.S. Provisional Patent Application is incorporated by reference in its entirety. Technical Field

[0002] The present invention relates to environmentally friendly paving bricks; more particularly, the present invention provides environmentally friendly paving bricks containing a large amount of recycled waste, which exhibit high strength, low wear resistance and low water absorption, and are suitable for large-scale production and application. Background Art

[0003] Modern society generates a large amount of waste that is difficult or impossible to recycle and costly to dispose of. As a metropolitan city, Hong Kong generates a large amount of waste every day, which in turn puts a huge load on the capacity of landfills. Statistics from the Hong Kong government show that although the amount of municipal solid waste recycled locally has increased by more than 20% year-on-year, the average daily landfill volume of solid waste still increased by 5.4% from 2020 to 2021, reaching an average daily landfill volume of 15,533 tons in 2021. Specifically, the daily landfill volume of plastic waste is about 2,300 tons, and the daily landfill volume of rubber waste is slightly less than 60 tons.

[0004] The amount of waste has grown exponentially in recent years due to the increased use of takeaway food containers, plastic utensils and non-recyclable masks.

[0005] As a result, Hong Kong, China has already filled and closed 13 landfills; the remaining three are expected to be filled by the 2030s.

[0006] Globally, municipal solid waste generation is estimated at around 2.1 billion tons in 2023, and is expected to increase to 3.8 billion tons by 2050. Meanwhile, only 9% of the 400 million tons of plastic waste generated globally was successfully recycled as of 2021. Unrecycled waste is either landfilled, incinerated, or leaks into the environment. The demand for waste recycling remains very high.

[0007] Hong Kong, China, and other urban centres, have large areas of paved areas, including sidewalks, driveways and alleys. For example, the total length of sidewalks in Hong Kong, China is well over 2,500 kilometres. As urban areas develop and become more walkable, the implementation of various urban development plans will increase the total length of paved pedestrian areas.

[0008] Since the 1980s, paving blocks have been increasingly used to pave sidewalks; as of 2023, about one-third of sidewalks in Hong Kong, China have been paved with paving blocks, with an estimated total of 66 million paving blocks used. The demand for paving blocks is expected to increase significantly in line with urban development and urban renewal plans, the need to expand pedestrian areas, and the repair and renewal of existing areas.

[0009] Attempts have been made to incorporate waste materials into various products such as paving blocks. However, existing paving blocks using waste materials do not have sufficient mechanical properties, such as load capacity, skid resistance and water absorption, to allow long-term use in high-traffic areas while optimizing pedestrian safety. The present invention addresses this need. Summary of the invention

[0010] The paving bricks of the present invention recycle non-biodegradable waste and convert them into environmentally friendly paving bricks, solving the mechanical property problems of prior art paving bricks. The paving bricks blend waste tire rubber, recycled plastic and recycled glass into a strong and wear-resistant cement-based material for pedestrian areas and sidewalks.

[0011] Specifically, the environmentally friendly reinforced recycled rubber-plastic-glass paving brick of the present invention comprises: 16.5 wt% to 17.5 wt% cement; 10 wt% to 15 wt% sand; 0.1 wt% to 0.5 wt% recycled waste tire rubber; 0.5 wt% to 5.0 wt% recycled plastic; 15 wt% to 20 wt% broken glass; 43 wt% to 47 wt% coarse aggregate; 5 wt% to 7 wt% water; and 0.1 wt% to 0.5 wt% high-efficiency water reducing agent. The compressive strength of the paving brick is at least 40 MPa.

[0012] According to the first aspect of the present invention, recycled waste tire rubber is pulverized into an average size of 100 to 500 μm and then used as a component of the paving block of the present invention.

[0013] In another embodiment, the average size of the cullet used in the paving blocks is less than 3.35 mm.

[0014] In another embodiment, the recycled plastic is physically processed through a rotary tumbler with ceramic media and further chemically processed with a binder.

[0015] In yet another embodiment, the adhesive is an acrylate polymer. More specifically, the acrylate polymer is selected from polyethyl acrylate, polybutyl acrylate, polyisobutyl acrylate or polyethylhexyl acrylate or a combination thereof.

[0016] In another embodiment, the high-efficiency water reducing agent added to the paving brick of the present invention is selected from polycarboxylate ether, sulfonated melamine formaldehyde, sulfonated naphthalene formaldehyde or lignin sulfonate or a combination thereof.

[0017] In yet another embodiment, the coarse aggregate is selected from non-recycled virgin aggregate, recycled construction aggregate, or a combination thereof.

[0018] In yet another embodiment, the unpolished slip resistance of the paving block is at least 70 USRV.

[0019] In another embodiment, the paving slab has a wear resistance of less than 23 mm.

[0020] In yet another embodiment, the paving block exhibits a water absorption of less than 5%. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Embodiments of the present invention are described in more detail below with reference to the accompanying drawings, in which:

[0022] Figure 1 The environmentally friendly paving bricks of the present invention are shown;

[0023] Figure 2 Optical microscope images showing the surface of a paving block according to the invention before (left) and after (right) processing by a grinder. DETAILED DESCRIPTION

[0024] This article describes a recycled rubber-plastic-glass paving block with a high content of recycled waste, including more than 20% by weight of waste tire rubber, recycled plastic and recycled glass, with higher waste recycling efficiency during the manufacturing process, providing opportunities for the application of recycled materials to meet the growing demand for waste recycling.

[0025] Specifically, waste tire rubber, recycled plastic and recycled glass used to make the paving bricks of the present invention can be pre-processed into the form of rubber powder, plastic pellets and crushed glass, respectively, to be incorporated into the bricks.

[0026] In order to further improve the mechanical properties of the paving blocks of the present invention, some of the recycled materials are subjected to physical and chemical treatments, respectively, which are not usually performed on prior art paving blocks made from recycled waste.

[0027] Additionally, the formulation of the paving blocks of the present invention allows for the replacement of conventional non-recycled virgin aggregates with recycled construction aggregates, which further increases waste recycling efficiency.

[0028] The cullet used as raw material for paving bricks in the present invention is made by crushing waste glass bottles. Although cullet generally has high compressive strength, the smooth surface of cullet may reduce the adhesion between cullet and cementitious materials. This situation can be improved by using cullet of smaller size to increase the surface area and thus improve the adhesion between cullet and cementitious materials.

[0029] The main component of glass is silicon dioxide, and it can react in the form of volcanic ash. Volcanic ash is an auxiliary cementitious material that can be added to concrete mixtures to improve the properties of concrete. When the cullet is small, its volcanic ash properties can be used to replace part of the cement. The cullet reacts with the hydration products of cement (i.e. calcium hydroxide) to increase the compressive strength of the concrete.

[0030] However, it is very costly to significantly reduce the size of cullet by crushing and grinding. Therefore, it is optimal to crush and grind the cullet to an average size of 2.36 mm in order to obtain appropriate compressive strength at a reasonable cost.

[0031] The recycled plastic used in the present invention is obtained by crushing waste plastic. The small plastic fragments can be used directly or can be made into a pellet form.

[0032] Recycled plastics are hydrophobic and usually have a smooth surface. Therefore, recycled plastics have a weaker bond with cementitious materials.

[0033] Thus, to make the paving bricks of the present invention, the recycled plastic is physically treated by using an industrial rotating drum with ceramic media. The surface will be polished and the roughness can be controlled by the tumbling time. This rough surface of the recycled plastic can increase the surface area for bonding with the cementitious material.

[0034] Additionally, the ground plastic is chemically treated with an acrylic adhesive to form a coating on the surface, which is a polyacrylate. The monomer of polyacrylate is acrylate. Different types of acrylates can be used, such as ethyl, butyl, isobutyl or ethylhexyl. Acrylic adhesives are hydrophilic because they contain carboxyl groups that are chemically highly polar. The acrylic adhesive coating can increase the adhesion between the recycled plastic and the cementitious material.

[0035] Although waste tire rubber is also a highly targeted material to be recycled and used in the paving blocks of the present invention, its incorporation may reduce strength when added to concrete. However, by controlling the amount used and using rubber powder of the right size, the reduction effect can be minimized.

[0036] Coarse rubber crumbs generally have a greater impact on strength. Fine rubber crumbs with a size of about 150 μm show minimal strength reduction. In addition, by introducing different aggregates of multiple sizes and selecting the appropriate aggregate size range and gradation, the packing density of concrete is improved and ultimately the compressive strength is increased.

[0037] Examples

[0038] Example 1 - Variation of plastic content

[0039] Studies were conducted to observe the mechanical properties of paving blocks, especially the compressive strength, by varying the plastic content in the formulation. The results are listed in Table 1 below.

[0040] Table 1: Effect of plastic content variation on compressive strength of paving slabs

[0041] From Table 1, it is observed that the general trend is that increasing plastic content generally decreases compressive strength.

[0042] Example 2 - Variation of Glass Content

[0043] Similarly, the glass content used to make the paving blocks in the present invention was adjusted, and the compressive strength was measured and compared in Table 2 below.

[0044] Table 2: Effect of glass content variation on compressive strength of paving blocks

[0045] The data in Table 2 show that varying the glass content within a limited range of 3% to 4% does not have a significant effect on the compressive strength of the paving blocks.

[0046] Example 3 - Variation of Rubber Content

[0047] The effect of the change in the content of recycled waste tire rubber in the paving bricks of the present invention was further studied. The results are shown in Table 3 below.

[0048] Table 3: Effect of rubber content variation on compressive strength of paving blocks

[0049] It should be noted that even a slight increase in the rubber content of the paving block will reduce the compressive strength of the paving block. In contrast, the effect of changing the content of recycled scrap tire rubber is more significant than that of changing the content of recycled plastic.

[0050] Example 4 - Use of recycled construction aggregate and additional mechanical property test results

[0051] According to the above results, it was found that the formula of 17.1 wt% cement, 10.3 wt% sand, 0.2 wt% rubber, 2.0 wt% plastic, 18.8 wt% glass, 45.1 wt% coarse aggregate, 6.3 wt% water and 0.2 wt% superplasticizer was optimal in terms of various mechanical properties, as shown in Table 4 below.

[0052] All the above tested paving block formulations used non-recycled virgin aggregate as the coarse aggregate of choice, while another study was conducted using the same formulation (17.1 wt% cement, 10.3 wt% sand, 0.2 wt% rubber, 2.0 wt% plastic, 18.8 wt% glass, 45.1 wt% coarse aggregate, 6.3 wt% water and 0.2 wt% superplasticizer, respectively), but replacing all virgin aggregate with recycled construction aggregate. The results are listed in Table 4.

[0053] Table 4: Effect of using recycled construction aggregates on various mechanical properties of paving blocks

[0054] It can be observed from Table 4 that replacing virgin aggregate with recycled construction aggregate results in a decrease in compressive strength. However, the ultimate compressive strength of 41.9 MPa is still acceptable for practical applications, providing reasonable safety in terms of load-bearing capacity. However, the wear resistance and unpolished slip resistance of the paving blocks using recycled construction aggregates are significantly improved, indicating that paving blocks using recycled construction aggregates are actually more suitable for application in areas with high humidity or rainfall, while having better durability.

[0055] The foregoing description of the present invention has been provided for the purpose of illustration and description. This description is not intended to be exhaustive or to limit the invention to the precise form disclosed. For those skilled in the art, many modifications and variations will be apparent.

[0056] The embodiment was chosen and described in order to best explain the principles of the invention and its practical application, thereby enabling others skilled in the art to understand the invention for various embodiments and with various modifications as are suited to the particular use contemplated.

Claims

1. An environmentally friendly reinforced recycled rubber-plastic-glass paving brick, comprising: 16.5 to 17.5 wt. % cement; 10 to 15 wt% sand; 0.1 wt% to 0.5 wt% recycled waste tire rubber; 0.5 wt% to 5.0 wt% recycled plastic; 15 to 20% by weight of cullet; 43 to 47 weight percent coarse aggregate; 5 to 7 wt % water; and 0.1 wt% to 0.5 wt% high-efficiency water reducer; The paving block has a compressive strength of at least 40 MPa.

2. The environmentally friendly reinforced recycled rubber-plastic-glass paving brick according to claim 1, wherein the recycled waste tire rubber is crushed into an average size of 100 to 500 μm.

3. The environmentally friendly reinforced recycled rubber-plastic-glass paving brick according to claim 1, wherein the average size of the broken glass is less than 3.35 mm.

4. The environmentally friendly reinforced recycled rubber-plastic-glass paving brick according to claim 1, wherein the recycled plastic is physically treated by a rotating drum with ceramic media and further chemically treated with a binder.

5. The environmentally friendly reinforced recycled rubber-plastic-glass paving brick according to claim 4, wherein the binder is an acrylic polymer.

6. The environmentally friendly reinforced recycled rubber-plastic-glass paving brick according to claim 5, wherein the acrylate polymer is selected from polyethyl acrylate, polybutyl acrylate, polyisobutyl acrylate or polyethylhexyl acrylate or a combination thereof.

7. The environmentally friendly reinforced recycled rubber-plastic-glass paving brick according to claim 1, wherein the high-efficiency water reducing agent is selected from polycarboxylate ether, sulfonated melamine formaldehyde, sulfonated naphthalene formaldehyde or lignin sulfonate or a combination thereof.

8. The environmentally friendly reinforced recycled rubber-plastic-glass paving block according to claim 1, wherein the coarse aggregate is selected from non-recycled virgin aggregate, recycled construction aggregate or a combination thereof.

9. The environmentally friendly reinforced recycled rubber-plastic-glass paving block according to claim 1, wherein the unpolished skid resistance of the paving block is at least 70 USRV.

10. The environmentally friendly reinforced recycled rubber-plastic-glass paving brick according to claim 1, wherein the wear resistance of the paving brick is less than 23 mm.

11. The environmentally friendly reinforced recycled rubber-plastic-glass paving brick according to claim 1, wherein the water absorption rate of the paving brick is less than 5%.

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