All-solid-waste low-carbon vegetation concrete and preparation method thereof

Abstract

The invention discloses all-solid-waste low-carbon vegetation concrete and a preparation method thereof, and belongs to the technical field of building materials. The all-solid-waste low-carbon vegetation concrete is prepared from a solid waste cementing material, solid waste coarse aggregate, fibers, a water reducing agent and water, the solid waste cementing material is prepared from the following raw materials in parts by mass: 55 to 90 parts of slag powder, 5 to 20 parts of industrial byproduct gypsum, 5 to 12 parts of rice hull ash, 5 to 15 parts of magnesium slag powder and 1 to 3 parts of carbide slag. The all-solid-waste low-carbon vegetation concrete designed by the invention has the advantages of low alkalinity, good durability, high utilization rate of solid waste resources and the like, and is low in total energy consumption and carbon emission due to no addition of cement. In an acid environment, the stability of a hydration product ettringite generated by the gelling system is higher than that of calcium hydroxide, and an obtained solid waste-based gelling material hardened body is more compact, can prevent hydrogen ions in the environment from entering the solid waste-based gelling material hardened body and has excellent acid corrosion resistance.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a low-carbon, all-solid-waste plant-based concrete and its preparation method. Background Technology

[0002] Vegetated concrete, as an eco-friendly building material, has been widely used in slope protection, riverbank protection, and other engineering fields due to its excellent coexistence with plants. Currently, this type of concrete mostly uses silicate cement as a binder. However, the cement industry itself is characterized by high energy consumption and high emissions, which contradicts the eco-friendly concept pursued by vegetated concrete. Furthermore, one of the main products of cement hydration is highly alkaline calcium hydroxide, resulting in a concrete pH value as high as 12-14, exceeding the pH range (6-9) suitable for most plant growth. Therefore, alkali reduction treatment is often necessary. However, while existing alkali reduction technologies can lower the alkalinity of concrete, they still have limitations in terms of efficiency and impact on other properties. On the one hand, alkali reduction treatment often fails to continuously inhibit the re-generation of calcium hydroxide during cement hydration. As cement hydration continues, the hydration product calcium hydroxide increases again, causing alkalinity to rise again and affecting plant survival rates. On the other hand, after alkalinity is reduced, the stability of hydration products is easily affected, potentially leading to decreased concrete strength and an increased risk of later cracking. In addition, since the hydration product calcium hydroxide is easily soluble in soft water environments and easily decomposes under acidic conditions, traditional vegetation concrete has poor durability in areas prone to soft water erosion (such as riverbanks) or areas with frequent acid rain, and further improvements are still needed. Summary of the Invention

[0003] The purpose of this invention is to provide a low-carbon, all-solid-waste vegetated concrete and its preparation method, thereby solving the aforementioned problems in the background art. The low-carbon, all-solid-waste vegetated concrete designed by this invention has advantages such as low alkalinity, good durability, and high utilization rate of solid waste resources. It does not contain cement, resulting in low overall energy consumption and carbon emissions. Under acidic conditions, the hydrated product ettringite generated by the cementing system of this invention exhibits greater stability than calcium hydroxide, and the resulting solid-waste-based cementitious material hardened body is more dense, preventing hydrogen ions from entering its interior, thus possessing excellent resistance to acid erosion.

[0004] To achieve the above objectives, the present invention provides the following technical solution: One of the technical solutions of this invention is to provide a low-carbon, plant-based concrete made entirely from solid waste, comprising solid waste cementitious materials, solid waste coarse aggregates, fibers, water-reducing agents, and water. The raw materials of the solid waste cementitious material, by mass parts, include: 55-90 parts of slag powder, 5-20 parts of industrial by-product gypsum, 5-12 parts of rice husk ash, 5-15 parts of magnesium slag powder, and 1-3 parts of calcium carbide slag.

[0005] Preferably, the mass ratio (aggregate-cement ratio) of the solid waste coarse aggregate to the solid waste cementitious material in the all-solid waste low-carbon vegetation concrete is 4-6; the mass ratio (water-cement ratio) of the water to the solid waste cementitious material is 0.2-0.3; and the amount of fiber added is 0.5%-1.5% of the concrete volume.

[0006] Preferably, the slag powder is S95 slag powder or S105 slag powder; The rice husk ash is a product of rice husk combustion. The preparation method is as follows: after calcining and activating the rice husk at 600℃-700℃, it is ground to a particle size of less than 15μm to obtain rice husk ash. The industrial by-product gypsum is desulfurized gypsum, phosphogypsum, or fluorogypsum.

[0007] Preferably, the magnesium slag powder is a byproduct of the Pidgeon process for magnesium smelting, with a γ-C2S content ≥65wt%; The calcium carbide slag is the waste residue produced after the hydrolysis of calcium carbide to obtain acetylene gas.

[0008] Preferably, the solid waste coarse aggregate is steel slag coarse aggregate with a particle size of 10mm-20mm.

[0009] Although both the steel slag and magnesium slag added in this invention contain dicalcium silicate, their functions are significantly different. The dicalcium silicate in the steel slag is β-C2S, which mainly improves hydraulic properties; while the dicalcium silicate in the magnesium slag is γ-C2S, which has higher carbonization activity. Therefore, the reason for adding magnesium slag is to use it as a carbonization sacrificial agent.

[0010] Preferably, the fiber is bagasse fiber or waste mask fiber; the bagasse fiber is obtained by crushing and processing bagasse, with an average fiber length of 1mm-5mm; the waste mask fiber is derived from disposable medical masks, which are recycled, disinfected, processed, and the main body is cut and crushed, with an average diameter of 20μm-40μm and an average length of 2-7mm.

[0011] Preferably, the bagasse fiber is soaked in a 4wt% sodium hydroxide solution for 8 hours before use, and then washed and dried; the waste mask fiber is soaked in a solution containing a silane coupling agent (vinyl silane coupling agent) for 20-30 minutes before use, and then washed, filtered, and dried.

[0012] Preferably, the water-reducing agent is a polycarboxylate water-reducing agent.

[0013] The second technical solution of the present invention provides a method for preparing the above-mentioned all-solid-waste low-carbon vegetated concrete, comprising the following steps: The raw materials are mixed and cured to obtain the all-solid-waste low-carbon vegetation concrete.

[0014] Preferably, the preparation method includes the following steps: The slag powder, industrial by-product gypsum, rice husk ash, magnesium slag powder, carbide slag and fiber are mixed in proportion to obtain a preliminary mixture; Add steel slag coarse aggregate and 60% water to the mixer and mix for 60 seconds. Then add 50% of the initial mixture and mix for 60 seconds to coat the surface of the steel slag coarse aggregate with solid waste cementitious material. Then add the remaining initial mixture, water and water-reducing agent and mix for 90 seconds. Cure to obtain the all-solid waste low-carbon vegetation concrete.

[0015] The beneficial technical effects of the present invention are as follows: The all-solid-waste low-carbon vegetated concrete designed in this invention has advantages such as low alkalinity, good durability, and high utilization rate of solid waste resources. The solid waste cementitious material in this invention is made from slag powder, industrial by-product gypsum, rice husk ash, magnesium slag powder, and carbide slag, without the addition of cement, resulting in low overall energy consumption and carbon emissions. The carbide slag provides a suitable alkaline environment for the system, promoting the dissolution of silicate and aluminate ions from the slag's glassy structure. These ions then combine with calcium and sulfate ions provided by gypsum, generating products mainly composed of ettringite and CSH gel, thus achieving matrix hardening. This reaction produces almost no strongly alkaline calcium hydroxide, achieving low alkalinity in the entire system, which is beneficial for plant survival and also enhances its resistance to leaching erosion. Under acidic conditions, the hydrated product ettringite generated by the cementing system of this invention has greater stability than calcium hydroxide, and the resulting solid waste-based cementitious material hardened body is more dense, hindering the entry of hydrogen ions from the environment into its interior, thus exhibiting excellent resistance to acid erosion. The main component of magnesium slag, γ-C2S, has higher carbonization activity than the hydration products of cementitious materials. Therefore, when exposed to CO2 in the environment, it can preferentially undergo carbonization reactions before the hydration products, acting as a carbonization sacrificial agent to protect the main hydration products and improve the matrix's resistance to carbonization decomposition. In addition, industrial by-product gypsum can provide essential nutrients for plant growth such as calcium, sulfur, and phosphorus, while slag and rice husk ash can provide silicon, which helps to enhance the uprightness of plant leaves and improve their resistance to lodging and pests.

[0016] This invention effectively improves the mechanical properties of all-solid-waste low-carbon vegetated concrete by optimizing the types and amounts of aggregates and fibers added. The surface of the steel slag coarse aggregate has a porous, honeycomb structure, which results in strong adhesion between it and the hardened cementitious material. Furthermore, the steel slag coarse aggregate contains active minerals such as dicalcium silicate (β-C2S), tricalcium silicate, and aluminoferrites, giving it certain hydraulic cementitious properties. The hydration reaction on its surface further strengthens the interfacial transition zone and optimizes interfacial bonding performance. The iron element that may dissolve from the steel slag is an essential nutrient for plants. The added fiber component is uniformly dispersed within the aggregate skeleton, acting as a bridge and crack inhibitor, effectively improving the toughness and crack resistance of the concrete. Detailed Implementation

[0017] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0018] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, are also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0019] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. It should be noted that any aspects of this invention not described in detail are conventional practices in the art and are not the focus of this invention.

[0020] The terms “comprising,” “including,” “having,” “containing,” etc., used in this invention are all open-ended terms, meaning that they include but are not limited to.

[0021] The slag powder used in the following embodiments and comparative examples of the present invention is S95 slag powder.

[0022] The magnesium slag powder used is a byproduct of the Pidgeon process for magnesium smelting, with a γ-C2S content of 73%.

[0023] The calcium carbide slag used is the waste residue produced after the hydrolysis of calcium carbide to obtain acetylene gas.

[0024] The particle size of the steel slag coarse aggregate used is 10mm-20mm.

[0025] The bagasse fiber used is obtained by crushing and processing bagasse, with an average fiber length of 3mm. Before use, it is soaked in a 4wt% sodium hydroxide solution for 8 hours and then washed and dried. The waste mask fiber used comes from disposable medical masks, which are recycled, disinfected, processed, and the main body is cut and crushed. The average diameter is 30μm and the average length is 5mm. Before use, it is soaked in a 2.0% vinyl silane coupling agent solution for 25 minutes and then washed, filtered, and dried.

[0026] The water-reducing agent used is a polycarboxylate water-reducing agent.

[0027] All raw materials used in the following embodiments and comparative examples of the present invention are commercially available products.

[0028] Example 1 A low-carbon, plant-based concrete made entirely from solid waste cementitious materials, steel slag coarse aggregate, fiber (bagasse fiber), water-reducing agent, and water; its aggregate-to-cement ratio is 4, and its water-to-cement ratio is 0.20; the amount of fiber added is 0.5% of the concrete volume.

[0029] The raw materials for solid waste cementitious materials, by mass fraction, are: 55 parts of slag powder, 20 parts of industrial by-product gypsum (desulfurized gypsum), 12 parts of rice husk ash, 10 parts of magnesium slag powder, and 3 parts of carbide slag.

[0030] The method for preparing rice husk ash is as follows: rice husks are calcined and activated at 650℃, and then ground to a particle size of less than 15μm to obtain rice husk ash.

[0031] The preparation method of this all-solid-waste low-carbon vegetation concrete is as follows: The slag powder, industrial by-product gypsum, rice husk ash, magnesium slag powder, carbide slag and fiber are mixed in proportion to obtain the initial mixture; Add steel slag coarse aggregate and 60% water to the mixer and mix for 60 seconds. Then add 50% of the initial mixture and mix for 60 seconds. Finally, add the remaining initial mixture, water and water-reducing agent and mix for 90 seconds. Cure to obtain all-solid waste low-carbon vegetation concrete.

[0032] Example 2 A low-carbon, plant-based concrete made entirely from solid waste cementitious materials, steel slag coarse aggregate, fiber (bagasse fiber), water-reducing agent, and water; its aggregate-cement ratio is 5, and its water-cement ratio is 0.28; the amount of fiber added is 1.0% of the concrete volume.

[0033] The raw materials for solid waste cementitious materials, by mass fraction, are: 84 parts of slag powder, 5 parts of industrial by-product gypsum (phosphogypsum), 5 parts of rice husk ash, 5 parts of magnesium slag powder, and 1 part of carbide slag.

[0034] The method for preparing rice husk ash is as follows: rice husks are calcined and activated at 700℃, and then ground to a particle size of less than 15μm to obtain rice husk ash.

[0035] The preparation method of this all-solid-waste low-carbon vegetation concrete is as follows: The slag powder, industrial by-product gypsum, rice husk ash, magnesium slag powder, carbide slag and fiber are mixed in proportion to obtain the initial mixture; Add steel slag coarse aggregate and 60% water to the mixer and mix for 60 seconds. Then add 50% of the initial mixture and mix for 60 seconds. Finally, add the remaining initial mixture, water and water-reducing agent and mix for 90 seconds. Cure to obtain all-solid waste low-carbon vegetation concrete.

[0036] Example 3 A low-carbon, plant-based concrete made entirely from solid waste cementitious materials, steel slag coarse aggregate, fiber (waste mask fiber), water-reducing agent, and water; its aggregate-to-cement ratio is 6, and its water-to-cement ratio is 0.30; the amount of fiber added is 1.5% of the concrete volume.

[0037] The raw materials for solid waste cementitious materials, by mass fraction, are: 62 parts of slag powder, 13 parts of industrial by-product gypsum (fluorogypsum), 8 parts of rice husk ash, 15 parts of magnesium slag powder, and 2 parts of carbide slag.

[0038] The method for preparing rice husk ash is as follows: rice husks are calcined and activated at 600℃, and then ground to a particle size of less than 15μm to obtain rice husk ash.

[0039] The preparation method of this all-solid-waste low-carbon vegetation concrete is as follows: The slag powder, industrial by-product gypsum, rice husk ash, magnesium slag powder, carbide slag and fiber are mixed in proportion to obtain the initial mixture; Add steel slag coarse aggregate and 60% water to the mixer and mix for 60 seconds. Then add 50% of the initial mixture and mix for 60 seconds. Finally, add the remaining initial mixture, water and water-reducing agent and mix for 90 seconds. Cure to obtain all-solid waste low-carbon vegetation concrete.

[0040] Comparative Example 1 The only difference from Example 1 is that the amount of slag powder added is changed from 55 parts to 45 parts.

[0041] Comparative Example 2 The only difference from Example 1 is that the addition of industrial by-product gypsum is omitted.

[0042] Comparative Example 3 The only difference from Example 1 is that the addition of rice husk ash is omitted.

[0043] Comparative Example 4 The only difference from Example 1 is that the addition of magnesium slag powder is omitted.

[0044] Comparative Example 5 The only difference from Example 1 is that the addition of carbide slag is omitted.

[0045] Comparative Example 6 The only difference from Example 1 is that the bagasse fiber was replaced with an equal mass of untreated bagasse fiber that was not soaked in a 4 wt% sodium hydroxide solution.

[0046] Comparative Example 7 The only difference from Example 1 is that the preparation method has been modified as follows: The slag powder, industrial by-product gypsum, rice husk ash, magnesium slag powder, carbide slag and fiber are mixed in proportion to obtain the initial mixture; Add steel slag coarse aggregate, initial mixture, water and water-reducing agent to the mixer and mix for 90 seconds. After curing, low-carbon vegetation concrete made entirely from solid waste is obtained.

[0047] Comparative Example 8 The only difference from Example 1 is that the solid waste cementitious material is replaced with an equal mass of ordinary Portland cement (grade Runfeng 42.5).

[0048] Effect verification 1. Testing Method The samples of each embodiment and comparative example were molded and cured to the specified age according to JC / T 2557-2020 "Vegetated Concrete".

[0049] After 7 days of standard curing, pH was tested according to the relevant requirements of JC / T 2557-2020. After 28 days of curing, compressive strength was tested. At the same time, dry and wet cycle tests were conducted with reference to the "Test Method for Performance of Autoclaved Aerated Concrete" to test compressive strength and calculate the dry and wet strength coefficient.

[0050] An acidic solution with a pH of 1.5 was prepared by mixing sulfuric acid and nitric acid solutions (molar ratio 9:1). Vegetated concrete that had been cured for 28 days was immersed in the acidic solution for 7 days. The concrete was then removed and tested for compressive strength loss rate and mass loss rate.

[0051] After 28 days of curing, the vegetated concrete was removed and filled with a nutrient substrate (a slurry of peat moss, compound fertilizer, and water in a 5:1:1 mass ratio, which was then grouted into the concrete pores; the compound fertilizer had a nitrogen, phosphorus, and potassium ratio of 9:6:4). A 4cm layer of natural soil and tall fescue seeds (30g / m²) was then laid on the surface. 2 They were placed outdoors in a natural environment to observe their growth.

[0052] 2. Test Results Table 1 The vegetated concrete samples from Examples 1-3, cured for 28 days, were dried at room temperature, crushed, and finely ground using a ball mill to obtain particles ranging from 0.125 mm to 0.25 mm. The leaching toxicity of heavy metals such as copper, zinc, cadmium, lead, chromium, beryllium, barium, nickel, silver, arsenic, and selenium was tested according to the relevant requirements of HJ 766-2015. The test results showed that all samples from Examples 1-3 met the standard limits, with beryllium, nickel, copper, selenium, silver, cadmium, lead, and chromium below the detection limits, zinc below 0.05 mg / L, barium below 0.2 mg / L, and arsenic below 0.001 mg / L.

[0053] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A low-carbon, plant-based concrete made entirely from solid waste, characterized in that, This includes solid waste cementitious materials, solid waste coarse aggregates, fibers, water-reducing agents, and water; The raw materials of the solid waste cementitious material, by mass parts, include: 55-90 parts of slag powder, 5-20 parts of industrial by-product gypsum, 5-12 parts of rice husk ash, 5-15 parts of magnesium slag powder, and 1-3 parts of calcium carbide slag.

2. The all-solid-waste low-carbon vegetation concrete according to claim 1, characterized in that, The mass ratio of solid waste coarse aggregate to solid waste cementitious material in the all-solid waste low-carbon vegetation concrete is 4-6; the mass ratio of water to solid waste cementitious material is 0.2-0.3; and the amount of fiber added is 0.5%-1.5% of the concrete volume.

3. The all-solid-waste low-carbon vegetation concrete according to claim 1, characterized in that, The slag powder is S95 slag powder or S105 slag powder; The industrial by-product gypsum is desulfurized gypsum, phosphogypsum, or fluorogypsum.

4. The all-solid-waste low-carbon vegetation concrete according to claim 1, characterized in that, The magnesium slag powder is a byproduct of the Pidgeon process for magnesium smelting, with a γ-C2S content ≥65wt%. The calcium carbide slag is the waste residue produced after the hydrolysis of calcium carbide to obtain acetylene gas.

5. The all-solid-waste low-carbon vegetated concrete according to claim 1, characterized in that, The solid waste coarse aggregate is steel slag coarse aggregate with a particle size of 10mm-20mm.

6. The all-solid-waste low-carbon vegetation concrete according to claim 1, characterized in that, The fiber is bagasse fiber or waste mask fiber.

7. The all-solid-waste low-carbon vegetation concrete according to claim 1, characterized in that, The water-reducing agent is a polycarboxylate water-reducing agent.

8. A method for preparing all-solid-waste low-carbon vegetated concrete according to any one of claims 1-7, characterized in that, Includes the following steps: The raw materials are mixed and cured to obtain the all-solid-waste low-carbon vegetation concrete.

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