Highly adsorptive alkali-activated pervious concrete

Abstract

This invention relates to a highly adsorbent alkali-activated permeable concrete, comprising 1180-1220 kg / m³ aggregate, 395-410 kg / m³ slag, 15-19% zeolite by weight of the slag, 10-16% activated carbon by weight of the slag, 18-20% solid alkali activator by weight of the slag, and 47-49% water by weight of the slag. This invention not only utilizes the solid alkali activator to improve operational safety and construction convenience, but also achieves a synergistic effect of high strength, high permeability, and high adsorption performance through optimized adsorption material ratios.

Description

Technical Field

[0001] This invention relates to the technical field of concrete, and in particular to a highly absorbent alkali-activated permeable concrete. Background Technology

[0002] Permeable concrete is a porous material with high porosity, enabling rainwater to infiltrate directly, thereby reducing total surface runoff and delaying peak runoff. It plays a crucial role in urban stormwater management and sponge city construction. With rapid urbanization, large areas of impermeable pavement such as roads and parking lots hinder the natural infiltration of rainwater, causing pollutants carried by rainwater to be discharged directly into surrounding water bodies without effective treatment. Heavy metals such as zinc, lead, copper, and cadmium are key pollutants in stormwater runoff due to their high toxicity, environmental persistence, and bioaccumulation in aquatic ecosystems. Traditional permeable concrete relies primarily on the pore structure between aggregates for rainwater infiltration, but its ability to remove dissolved heavy metals is limited. Therefore, there is an urgent need to introduce high-performance adsorption materials to improve its pollution control efficiency.

[0003] In recent years, slag-based alkali-activated concrete has become an environmentally friendly alternative to traditional silicate cement-based materials due to its low heat of hydration, high long-term strength, and strong durability. Slag, as an industrial byproduct, does not require high-temperature calcination and can form a cementitious system at room temperature through alkali activation, helping to reduce energy consumption and carbon emissions during concrete production. In permeable concrete, the introduction of porous adsorbent materials such as zeolite and activated carbon can synergistically leverage the cation exchange capacity of zeolite and the physical adsorption capacity of activated carbon, thereby achieving effective capture of heavy metals. However, the mix design of alkali-activated permeable concrete in existing technologies still has several shortcomings. On the one hand, traditional alkali-activated cementitious materials are mostly two-component systems, typically relying on strong liquid alkalis such as sodium hydroxide as activators. These solutions are highly corrosive, making operation difficult and posing safety hazards during transportation and construction, hindering their widespread application in engineering projects. On the other hand, the proportion of zeolite and activated carbon as adsorption functional components lacks systematic optimization, making it difficult to achieve efficient heavy metal removal while ensuring permeability and mechanical strength. The synergistic effect between adsorbent materials, cementitious materials, and aggregates in the existing mix design has not been fully utilized, resulting in the inability to balance the comprehensive performance of concrete (compressive strength, permeability coefficient, and heavy metal adsorption efficiency). Summary of the Invention

[0004] The problem to be solved by the present invention is to provide a highly adsorbent alkali-activated permeable concrete that addresses the above-mentioned shortcomings of the prior art. It has the advantages of improving operational safety and construction convenience by using solid alkali activators, and achieving a synergistic effect of high strength, high permeability and high adsorption performance by optimizing the ratio of adsorbent materials.

[0005] The above-mentioned objective of this invention is achieved through the following technical solutions: A highly adsorbent alkali-activated permeable concrete comprises 1180~1220 kg / m³ aggregate, 395~410 kg / m³ slag, 15~19% zeolite by weight of the slag, 10~16% activated carbon by weight of the slag, 18~20% solid alkali activator by weight of the slag, and 47~49% water by weight of the slag.

[0006] Furthermore, the aggregate is crushed stone with a particle size range of 4.75~7.50mm.

[0007] Furthermore, the Blaine specific surface area of ​​the slag, zeolite, and activated carbon is ≥4500 cm². 2 / g.

[0008] Furthermore, the preparation process of the activated carbon includes: chemically activating almond shells in a phosphoric acid solution; after the reaction is completed, carbonizing-activating reaction is carried out in a nitrogen atmosphere; and after the reaction is completed, post-treatment is performed to obtain activated carbon.

[0009] Furthermore, in the chemical-activation reaction step, the mass concentration of the phosphoric acid solution is 45-55%, and the mass ratio of almond shells to phosphoric acid is 1:(3-4).

[0010] Furthermore, in the chemical-activation reaction step, the almond shells are pre-washed, dried, and crushed to increase their specific surface area. They are then soaked in a phosphoric acid solution and stirred continuously at room temperature for 20-30 hours. The almond shells are stirred at low speed and controlled to float on the surface of the solution to ensure uniform penetration of phosphoric acid into the almond shells and complete the chemical-activation reaction, resulting in impregnated almond shells.

[0011] Furthermore, in the carbonization-activation reaction step, the impregnated almond shells obtained from the chemical-activation reaction are first transferred to a cylindrical steel furnace, and then subjected to controlled thermal decomposition at 500~700℃ for 120~160 minutes in a nitrogen atmosphere, with the nitrogen concentration controlled to be no less than 99.99%, in order to complete the carbonization-activation reaction and obtain carbonized almond shells.

[0012] Furthermore, in the post-processing step, the carbonized almond shells obtained from the carbonization-activation reaction are first washed with water until neutral to remove residual phosphoric acid, then dried at 100-110°C for 20-30 hours, and finely ground to a Blaine surface area ≥4500 cm². 2 / g, to obtain activated carbon.

[0013] Furthermore, the solid alkali activator is sodium silicate pentahydrate with a particle size range of 600~1600μm.

[0014] Furthermore, the concrete preparation process includes first mixing aggregates, mineral powder, zeolite, activated carbon and solid alkali activator, then adding water and continuing to mix to obtain concrete.

[0015] In summary, the beneficial technical effects of the present invention are as follows: In summary, the present invention has the following beneficial effects: 1. Because this invention uses slag as a cementing material and sodium silicate pentahydrate with a particle size range of 600~1600 μm as a solid alkali activator to replace the traditional highly corrosive liquid alkali activator, while controlling the zeolite content to 15~19% of the slag mass and the activated carbon content to 10%~16% of the slag mass, and optimizing the water-cement ratio to 0.47~0.49, the reaction of concrete during alkali activation is mild and controllable, avoiding the safety hazards of liquid alkali activators in transportation and construction, and improving the ease of operation and engineering applicability. On this basis, zeolite and activated carbon synergistically exert cation exchange and physical adsorption effects, achieving efficient removal of various heavy metal ions such as cadmium, lead, copper, and zinc while ensuring the pore structure and mechanical properties of permeable concrete, and obtaining a comprehensive effect of synergistic improvement in high strength, high permeability, and high adsorption performance. 2. In this invention, activated carbon prepared from almond shells through a combination of phosphoric acid chemical activation and carbonization-activation is preferred. Phosphoric acid chemical activation promotes the development of microporous structure, followed by high-temperature carbonization-activation treatment in a nitrogen atmosphere. This process gives the activated carbon a well-developed microporous structure and a Blaine surface area of ​​not less than 4500 cm² / g, significantly enhancing its physical adsorption capacity for dissolved heavy metals. At the same time, using almond shells as biomass raw materials realizes the resource utilization of agricultural waste, achieving the dual benefits of improved adsorption performance and the development of materials with low environmental impact. 3. The concrete preparation method of the present invention involves first thoroughly mixing aggregates, slag, zeolite, activated carbon, and solid alkali activator in a dry state to ensure uniform dispersion of each solid component in the system, and then adding water for wet mixing. This avoids the problem of local agglomeration of adsorbent materials or uneven distribution caused by premature contact with water, and ensures that the adsorbent functional components form a uniform and continuous adsorption interface inside the concrete. Therefore, stable permeability and uniform heavy metal adsorption effect are obtained. Attached Figure Description

[0016] Figure 1 This is a model diagram of aggregate gradation in Embodiment 1 of the present invention.

[0017] Figure 2 This is a slag gradation model diagram of Embodiment 1 of the present invention.

[0018] Figure 3 These are test results of the heavy metal adsorption performance of some concrete specimens prepared in Examples 4 to 39 of this invention. Detailed Implementation

[0019] To make the technical means, creative features, objectives and effects of this invention clearer and easier to understand, the invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0020] Example 1: A highly adsorbent alkali-activated permeable concrete disclosed in this invention comprises 1200 kg / m³ aggregate, 400 kg / m³ slag, zeolite accounting for 15% of the total weight of the slag, activated carbon accounting for 10% of the total weight of the slag, a solid alkali activator accounting for 20% of the total weight of the slag, and water accounting for 48% of the total weight of the slag. Wherein, Aggregate: Crushed stone with a particle size range of 4.75~7.50mm, gradation model as follows Figure 1 As shown; Slag: Blaine specific surface area ≥ 4500 cm² 2 / g, gradation model as follows Figure 2 As shown; Zeolite: Burgh's specific surface area ≥ 4500 cm² 2 / g, the gradation and particle shape characteristics of slag, zeolite and activated carbon are the same, which makes it easier to mix more evenly; The preparation process of activated carbon includes, S1 The almond shells are pre-cleaned, dried and crushed to increase the specific surface area of ​​the almond shells. Then they are soaked in phosphoric acid solution and stirred continuously at room temperature for 24 hours. The almond shells are stirred at low speed and controlled to float on the surface of the solution to complete the uniform penetration of phosphoric acid into the almond shells and complete the chemical-activation reaction to obtain impregnated almond shells. S2 first transfers the impregnated almond shells obtained from the chemical-activation reaction to a cylindrical steel furnace, and then performs a controlled thermal decomposition at 600℃ for 120~160 minutes in a nitrogen atmosphere, controlling the nitrogen concentration to be no less than 99.99% to complete the carbonization-activation reaction and obtain carbonized almond shells. S3 first washes the carbonized almond shells obtained from the carbonization-activation reaction until neutral with water to remove residual phosphoric acid, then dries them at 105℃ for 24 hours, and finely grinds them until the Blaine surface area is ≥4500 cm². 2 / g, to obtain activated carbon; Solid alkali activator: Sodium silicate pentahydrate (purchased from Shanghai Yueda) with a particle size range of 600~1600 μm. The particle size distribution is as follows: >1600 μm (coarse / oversized): ≤ 2% (upper limit control), 1250~1600 μm: 15~30% (coarse particle segment), 800~1250 μm: 40~65% (main peak / mainstream particle size), 600~800 μm: 15~30% (fine particle segment), <600 μm (fine powder): ≤ 2% (lower limit control). The concrete preparation process includes first mixing aggregates, mineral powder, zeolite, activated carbon and solid alkali activator, then adding water and continuing to mix until the concrete is obtained.

[0021] Example 2: This is a highly adsorbent alkali-activated permeable concrete disclosed in this invention. The difference from Example 1 is that the preparation process of activated carbon includes... S1 The almond shells are pre-cleaned, dried and crushed to increase the specific surface area of ​​the almond shells. Then they are soaked in phosphoric acid solution and stirred continuously at room temperature for 20 hours. The almond shells are stirred at low speed and controlled to float on the surface of the solution to complete the uniform penetration of phosphoric acid into the almond shells and complete the chemical-activation reaction to obtain impregnated almond shells. S2 first transfers the impregnated almond shells obtained from the chemical-activation reaction into a cylindrical steel furnace, and then performs a controlled thermal decomposition at 500℃ for 120 minutes in a nitrogen atmosphere, controlling the nitrogen concentration to be no less than 99.99% to complete the carbonization-activation reaction and obtain carbonized almond shells. S3 first washes the carbonized almond shells obtained from the carbonization-activation reaction until neutral with water to remove residual phosphoric acid, then dries them at 100℃ for 20 hours, and finely grinds them until the Blaine surface area is ≥4500 cm². 2 / g, to obtain activated carbon.

[0022] Example 3: This is a highly adsorbent alkali-activated permeable concrete disclosed in this invention. The difference from Example 1 is that the preparation process of activated carbon includes... S1 The almond shells are pre-cleaned, dried and crushed to increase the specific surface area of ​​the almond shells. Then they are soaked in phosphoric acid solution and stirred continuously at room temperature for 30 hours. The almond shells are stirred at low speed and controlled to float on the surface of the solution to complete the uniform penetration of phosphoric acid into the almond shells and complete the chemical-activation reaction to obtain impregnated almond shells. S2 first transfers the impregnated almond shells obtained from the chemical-activation reaction to a cylindrical steel furnace, and then performs a controlled thermal decomposition at 700℃ for 160 minutes in a nitrogen atmosphere, controlling the nitrogen concentration to be no less than 99.99% to complete the carbonization-activation reaction and obtain carbonized almond shells. S3 first washes the carbonized almond shells obtained from the carbonization-activation reaction until neutral with water to remove residual phosphoric acid, then dries them at 110℃ for 30 hours, and finely grinds them until the Blaine surface area is ≥4500 cm². 2 / g, to obtain activated carbon.

[0023] Examples 4-39: These are examples of highly adsorbent alkali-activated permeable concrete disclosed in this invention. The difference from Example 1 is that the dosage of activated carbon and zeolite is selected in the range of 5% to 30% of the slag mass, with a gradient of 5%. That is, the activated carbon dosage is 5%, 10%, 15%, 20%, 25%, and 30% of slag, and the zeolite dosage is 5%, 10%, 15%, 20%, 25%, and 30% of slag, respectively. The slag mass is 400 kg / m³, the water-cement ratio is 0.48, and the solid alkali activator dosage is 20% of slag, for a total of 36 groups.

[0024] Concrete samples prepared in Examples 4-39 were cured for 7 days to obtain concrete specimens. The properties of the concrete specimens were then tested, and some test results are shown below. Figure 3 As shown.

[0025] Combination Figure 3 It can be seen that, 1) The adsorption efficiencies of all formulations fall within the following ranges: cadmium (90-98%), zinc (88-97%), copper (85-96%), chromium (85-92%), and lead (60-70%). The last three formulations are optimized. The M400AC15Z20 formulation exhibits the highest overall adsorption efficiency, achieving removal rates of 97% for cadmium, 96% for copper, 95% for zinc, 92% for chromium, and 70% for lead. 2) Permeability coefficient: 2.5 × 10⁻⁶ −3 ~3.5×10 −3 Between cm / s; among them, M400AC5, 3.2×10 −3 cm / s, M400AC10, 3.4×10 -3 cm / s, M400AC15, 3.5×10 -3 cm / s, M400Z10, 2.7×10 -3 cm / s, M400Z15, 2.5×10 -3 cm / s, M400AC5Z20, 2.6×10 -3 cm / s, M400AC10Z10, 2.9×10 -3 cm / s, M400AC15Z20, 2.8×10 -3 cm / s 3) Compressive strength: The compressive strength of the optimized mix proportion is not less than 20 MPa; among which, M400AC5, 17.5 MPa, M400AC10, 18.3 MPa, M400AC15, 18.8 MPa, M400Z10, 18.9 MPa, M400Z15, 19.2 MPa, M400AC5Z20, 20.1 MPa, M400AC10Z10, 20.4 MPa, M400AC15Z20, 20.6 MPa.

[0026] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A highly absorbent alkali-activated permeable concrete, characterized in that: It includes 1180~1220 kg / m³ of aggregate, 395~410 kg / m³ of slag, 15~19% of zeolite by weight of the slag, 10~16% of activated carbon by weight of the slag, 18~20% of solid alkali activator by weight of the slag, and 47~49% of water by weight of the slag.

2. The highly absorbent alkali-activated permeable concrete according to claim 1, characterized in that: The aggregate is crushed stone with a particle size range of 4.75~7.50mm.

3. The highly absorbent alkali-activated permeable concrete according to claim 1, characterized in that: The Blaine specific surface area of ​​the slag, zeolite, and activated carbon is ≥4500 cm². 2 / g.

4. The highly absorbent alkali-activated permeable concrete according to claim 1, characterized in that: The preparation process of the activated carbon includes: chemically activating almond shells in a phosphoric acid solution; after the reaction, carbonizing-activating reaction is carried out in a nitrogen atmosphere; and after post-treatment, activated carbon is obtained.

5. The highly absorbent alkali-activated permeable concrete according to claim 4, characterized in that: In the chemical-activation reaction step, the mass concentration of the phosphoric acid solution is 45-55%, and the mass ratio of almond shell to phosphoric acid is 1:(3-4).

6. The highly absorbent alkali-activated permeable concrete according to claim 4, characterized in that: In the chemical-activation reaction step, the almond shells are pre-washed, dried and crushed to increase the specific surface area of ​​the almond shells, and then soaked in phosphoric acid solution. The mixture is stirred continuously at room temperature for 20-30 hours. The almond shells are stirred at low speed and controlled to float on the surface of the solution to complete the uniform penetration of phosphoric acid into the almond shells and complete the chemical-activation reaction to obtain impregnated almond shells.

7. The highly absorbent alkali-activated permeable concrete according to claim 4, characterized in that: In the carbonization-activation reaction step, the impregnated almond shells obtained from the chemical-activation reaction are first transferred to a cylindrical steel furnace, and then subjected to controlled thermal decomposition at 500~700℃ for 120~160 minutes in a nitrogen atmosphere, with the nitrogen concentration controlled to be no less than 99.99% to complete the carbonization-activation reaction and obtain carbonized almond shells.

8. The highly absorbent alkali-activated permeable concrete according to claim 4, characterized in that: In the post-processing step, the carbonized almond shells obtained from the carbonization-activation reaction are first washed with water until neutral to remove residual phosphoric acid, then dried at 100-110°C for 20-30 hours, and finely ground to a Blaine surface area ≥4500 cm². 2 / g, to obtain activated carbon.

9. The highly absorbent alkali-activated permeable concrete according to claim 1, characterized in that: The solid alkali activator is sodium silicate pentahydrate with a particle size range of 600~1600μm.

10. The highly adsorbent alkali-activated permeable concrete according to claim 1, characterized in that: The concrete preparation process includes first mixing aggregates, mineral powder, zeolite, activated carbon and solid alkali activator, then adding water and continuing to mix to obtain concrete.

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