A kind of active water permeable brick for reducing rainwater nitrogen and phosphorus pollutants and a preparation method thereof

Abstract

This invention discloses an active permeable brick for reducing nitrogen and phosphorus pollutants in rainwater and its preparation method. (1) Limestone is mechanically vibrated and sieved to obtain limestone with a particle size of 1-9 mm, which is then washed and air-dried. (2) Limestone, fly ash, silicate cement, water, and water-reducing agent are weighed, mixed, and stirred evenly to obtain a mixture. (3) The mixture is filled into a mold for molding. (4) The molded brick is cured along with the mold. (5) The brick in the mold is demolded and then cured again to obtain the finished active permeable brick. This invention addresses the fact that most current research on permeable brick preparation processes only optimizes its physical properties (compressive strength, permeability coefficient, etc.) while neglecting to optimize its nitrogen and phosphorus removal performance, thus failing to meet the requirements of sponge cities for reducing nitrogen and phosphorus pollutants in initial rainwater. Therefore, the active permeable brick prepared by the method of this invention not only has high compressive strength and good permeability but also effectively reduces nitrogen and phosphorus pollutants in initial rainwater.

Description

Technical Field

[0001] This invention belongs to the field of permeable building materials technology, specifically relating to an active permeable brick for reducing nitrogen and phosphorus pollutants in rainwater and its preparation method. Background Technology

[0002] Rainfall runoff carries nitrogen and phosphorus pollutants from the underlying surfaces of urban roads into surrounding water bodies, causing pollution and contributing significantly to eutrophication of urban rivers and lakes. Furthermore, with urbanization, paved roads prevent rainwater from infiltrating and replenishing groundwater, exacerbating water shortages and triggering urban flooding.

[0003] Permeable bricks, as a permeable surface material with good pressure resistance and water permeability, can effectively promote rainwater infiltration. Currently, most research on the manufacturing process of permeable bricks focuses on optimizing their physical properties (compressive strength, permeability coefficient, etc.). However, as a crucial barrier for rainwater infiltration, permeable bricks with good nitrogen and phosphorus removal properties could potentially play a positive role in the treatment of water pollution. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide an active permeable brick for reducing nitrogen and phosphorus pollutants in rainwater and its preparation method, thus solving the problems mentioned in the background art.

[0005] One of the technical solutions adopted by this invention to solve its technical problem is: a method for preparing an active permeable brick for reducing nitrogen and phosphorus pollutants in rainwater, comprising the following steps:

[0006] (1) The limestone is mechanically vibrated and screened to obtain limestone with a particle size of 1-9 mm, and then washed and air-dried.

[0007] (2) Set the water-cement ratio to be 0.22~0.34, the target porosity to be 10%~25%, the aggregate particle size to be 1-9mm, the fly ash content to be 5~20% of the total cement mass, and the water-reducing agent content to be 1% of the water mass as parameters. Calculate the amount of each material using the volume method. The ratio of aggregate, cement, fly ash, water, and water-reducing agent is 1514~1731g: 467~746g: 36~145g: 121~194g: 1.21~1.94g;

[0008] (3) Weigh the corresponding mass of limestone (aggregate), fly ash, silicate cement, water, and water-reducing agent, mix and stir evenly to obtain a mixture;

[0009] (4) The mixture is filled into a mold and shaped;

[0010] (5) Curing the formed bricks together with the mold;

[0011] (6) After demolding the bricks in the mold, continue curing to obtain the finished active permeable brick.

[0012] In a preferred embodiment of the present invention, in step (1), the particle size of limestone is 3-6 mm.

[0013] In a preferred embodiment of the present invention, in step (2), the fly ash grade is Class II.

[0014] In a preferred embodiment of the present invention, in step (2), the water-cement ratio is 0.26, the target porosity is 15%, the aggregate particle size is 3-6mm, the fly ash content accounts for 20% of the cement mass, the water-reducing agent content accounts for 1% of the water mass, and the calculated ratio of aggregate, cement, fly ash, water and water-reducing agent is 1731g:580g:145g:151g:1.51g.

[0015] In a preferred embodiment of the present invention, in step (3), the stirring time is 1 minute, until the surface of the aggregate is completely covered by silicate cement and exhibits a metallic luster.

[0016] In a preferred embodiment of the present invention, in step (4), the mixture is filled into the mold in layers, and the mold is vibrated at high frequency and low amplitude after each layer of mixture is filled. Then, the mixture is tamped evenly with a tamping rod.

[0017] In a preferred embodiment of the present invention, in step (4), the material is filled with a layer of material and the high-frequency low-amplitude vibration mold is used for 10 seconds, and the material is tamped 50 times with a tamping rod.

[0018] In a preferred embodiment of the present invention, in step (5), the formed bricks together with the mold are sent into a concrete curing box with a temperature of 20±2℃ and a relative humidity of more than 95% for curing for 1 day.

[0019] In a preferred embodiment of the present invention, in step (6), the brick in the mold is demolded and then sent into the concrete curing box for curing. After curing for 28 days, the active permeable brick product is obtained.

[0020] The second technical solution adopted by the present invention to solve its technical problem is: to provide an active permeable brick for reducing nitrogen and phosphorus pollutants in rainwater, which is prepared by the above method and has a size of 200×100×60mm.

[0021] Compared with the prior art, this technical solution has the following advantages:

[0022] 1. The active permeable bricks prepared by this invention have high compressive strength and good water permeability;

[0023] 2. Based on the optimized physical properties of traditional permeable bricks, this invention further optimizes their nitrogen and phosphorus removal performance, which can effectively reduce nitrogen and phosphorus pollutants in water bodies and alleviate the problem of eutrophication in urban rivers and lakes.

[0024] 3. This invention utilizes limestone's high hardness, stable chemical properties, and certain phosphorus removal capacity as a phosphorus removal matrix aggregate; it also utilizes fly ash's pozzolanic activity, which, when introduced into concrete mixing, effectively improves brick strength. Furthermore, fly ash has a large specific surface area and high surface energy, and contains metal silicates such as Ca and Al, exhibiting good phosphorus removal performance and a certain ammonia nitrogen removal capacity. Additionally, by replacing a portion of cement with fly ash, raw material costs are saved, and the goal of solid waste resource utilization is achieved.

[0025] 4. This invention uses a non-sintering process, which saves energy, has low preparation cost, and is pollution-free during the preparation process. Attached Figure Description

[0026] Figure 1 Figure 1 shows the test results of permeability coefficient and compressive strength of active permeable bricks prepared with different water-cement ratios.

[0027] Figure 2 Figure 1 shows the test results of permeability coefficient and compressive strength of active permeable bricks prepared for different target porosities;

[0028] Figure 3 Figure 1 shows the test results of permeability coefficient and compressive strength of active permeable bricks prepared with different aggregate particle sizes.

[0029] Figure 4 Figure 1 shows the test results of permeability coefficient and compressive strength of active permeable bricks prepared with different fly ash contents;

[0030] Figure 5 The orthophosphate removal effect of activated permeable bricks prepared with different water-cement ratios;

[0031] Figure 6 The ammonia nitrogen removal effect of activated permeable bricks prepared with different water-cement ratios;

[0032] Figure 7 The orthophosphate removal effect of activated permeable bricks prepared for different target porosities;

[0033] Figure 8 The ammonia nitrogen removal effect of activated permeable bricks prepared for different target porosities;

[0034] Figure 9 The orthophosphate removal effect of activated permeable bricks prepared with different aggregate particle sizes;

[0035] Figure 10The ammonia nitrogen removal effect of activated permeable bricks prepared with different aggregate particle sizes;

[0036] Figure 11 The orthophosphate removal effect of activated permeable bricks prepared with different fly ash admixtures;

[0037] Figure 12 The ammonia nitrogen removal effect of activated permeable bricks prepared with different fly ash admixtures. Detailed Implementation

[0038] In the following description of the embodiments, the water-cement ratio (W / C), target porosity (P), aggregate particle size (D), and fly ash content (C) are specified. f ).

[0039] The operation and calculation methods for the compressive strength and permeability coefficient tests of active permeable bricks shall be implemented in accordance with the relevant contents of GB / T 25993-2010 "Permeable Pavement Bricks and Permeable Pavement Panels" and CJ / T 400-2012 "Recycled Aggregate Pavement Bricks and Permeable Bricks".

[0040] The nitrogen and phosphorus reduction effect of activated permeable bricks was determined through an indoor simulated rainfall experiment. The experiment was conducted in a self-made transparent plexiglass tank (30cm×30cm×25cm). The rainwater quality was simulated based on the highest nitrogen and phosphorus pollution concentrations characteristic of rainfall runoff in Xiamen City, with an ammonia nitrogen concentration of 10 mg / L and an orthophosphate concentration of 4 mg / L. The rainfall intensity was determined according to DB3502 / Z "Xiamen City Rainstorm Intensity Formula and Design Rainstorm Pattern," using a return period P=20 years, a rainfall duration t=60 min, and a rainfall intensity of 82 mm / h. Samples were taken from the outlet of the device every 5 minutes from the start of rainfall, for a total of 12 samples. The ammonia nitrogen and orthophosphate concentrations in the water samples were measured after the experiment.

[0041] Ammonia nitrogen in water samples was determined using Nessler's reagent spectrophotometry (HJ 535-2009), and orthophosphate was determined using the molybdenum-antimony anti-magnetic spectrophotometric method (GB 11893-89).

[0042] The preparation method of the active permeable bricks in the following embodiments adopts the following steps:

[0043] (1) The limestone is mechanically vibrated and screened to obtain limestone of the target particle size, and then washed with tap water and dried in the shade for later use.

[0044] (2) Set the optimization range for each parameter and calculate the amount of each material according to the volume method;

[0045] (3) Weigh out the corresponding mass of limestone, fly ash, silicate cement, water and water-reducing agent respectively, add them to the mixer and stir for 1 minute until the surface of the aggregate is completely covered by cement and has a metallic color, to obtain the mixture.

[0046] (4) Fill the steel mold with the mixed material in 3 layers. After each layer of material is filled, vibrate the mold with high frequency and low amplitude for 10 seconds. Then, tamp the material with a tamping rod 50 times to tamp the material evenly.

[0047] (5) The bricks after tamping and molding are sent into a concrete curing box with a temperature of 20±2℃ and a relative humidity of more than 95%.

[0048] (6) After curing for 1 day, the bricks in the mold are demolded and sent back to the curing box for curing. After curing for 28 days, the active permeable bricks are obtained.

[0049] Examples 1-4:

[0050] The water-cement ratio (W / C) was changed as follows:

[0051] 1#: P=20%, D=3-6mm, Cf=10%, W / C=0.22;

[0052] 2#: P=20%, D=3-6mm, Cf=10%, W / C=0.26;

[0053] 3#: P=20%, D=3-6mm, Cf=10%, W / C=0.30;

[0054] 4#: P=20%, D=3-6mm, Cf=10%, W / C=0.34;

[0055] Examples 5-8:

[0056] The target porosity changes are numbered as follows:

[0057] 5#: W / C=0.26, D=3-6mm, Cf=10%, P=10%;

[0058] 6#: W / C=0.26, D=3-6mm, Cf=10%, P=15%;

[0059] 7#: W / C=0.26, D=3-6mm, Cf=10%, P=20%;

[0060] 8#: W / C=0.26, D=3-6mm, Cf=10%, P=25%;

[0061] Examples 9-11:

[0062] Aggregate particle size variations, numbered as follows:

[0063] 9#: W / C=0.26, P=15%, Cf=10%, D=1-3mm;

[0064] 10#: W / C=0.26, P=15%, Cf=10%, D=3-6mm;

[0065] 11#: W / C=0.26, P=15%, Cf=10%, D=6-9mm;

[0066] Examples 12-15:

[0067] The changes in fly ash content are numbered as follows;

[0068] 12#: W / C=0.26, P=15%, D=3-6mm, Cf=5%;

[0069] 13#: W / C=0.26, P=15%, D=3-6mm, Cf=10%;

[0070] 14#: W / C=0.26, P=15%, D=3-6mm, Cf=15%;

[0071] 15#: W / C=0.26, P=15%, D=3-6mm, Cf=20%

[0072] The performance of Examples 1-15 described above was tested, and the results are as follows:

[0073] I. Compressive strength of active permeable bricks:

[0074] The pressures for #1 through #4 are 16.18, 20.36, 22.07, and 23.38 MPa, respectively.

[0075] The values ​​for #5 to #8 are 35.07, 28.64, 20.36, and 14.89 MPa, respectively.

[0076] The values ​​for #9 to #11 are 29.40, 28.64, and 23.13 MPa, respectively.

[0077] The values ​​for #12 to #15 are 26.38, 28.64, 26.57, and 24.02 MPa, respectively.

[0078] II. Permeability coefficient of permeable bricks at standard temperature (15℃):

[0079] Sizes 1# to 4# are 1.96cm, 2.83cm, 3.35cm, and 3.22cm respectively. -2 / s;

[0080] Sizes 5# to 8# are 1.91cm, 2.43cm, 2.83cm, and 3.53cm respectively. -2 / s;

[0081] Sizes 9 through 11 are 1.79cm, 2.43cm, and 4.06cm respectively. -2 / s.

[0082] Depend on Figure 1 It can be seen that the compressive strength and permeability coefficient of permeable bricks prepared with different water-cement ratios vary significantly. As the water-cement ratio increases, the permeability coefficient of the permeable bricks first increases and then decreases. Permeable bricks prepared with a water-cement ratio below 0.22 no longer meet the Class A permeability requirements. Figure 5 It can be seen that the orthophosphate removal rates of permeable bricks prepared with different water-cement ratios, from high to low, are: W / C=0.22, W / C=0.26, W / C=0.34, and W / C=0.30, with average orthophosphate reduction rates of 59.91%, 47.67%, 42.28%, and 34.08%, respectively. Figure 6 It can be seen that the ammonia nitrogen removal rate of permeable bricks prepared with different water-cement ratios is relatively low. The average ammonia nitrogen reduction rates for W / C = 0.22-0.34 are 4.27%, 7.89%, 7.61%, and 12.85%, respectively. Therefore, the embodiment with a water-cement ratio of 0.26 is preferred.

[0083] Depend on Figure 2 It can be seen that the compressive strength and permeability coefficient of permeable bricks prepared with different target porosities vary significantly. As the target porosity increases, the permeability coefficient of the permeable bricks gradually increases. Permeable bricks prepared with a target porosity below 10% no longer meet the Class A permeability requirements. Figure 7 It can be seen that the orthophosphate removal rates of permeable bricks prepared with different target porosities, from high to low, are: P=10%, P=15%, P=20%, P=25%, with average orthophosphate reduction rates of 56.48%, 54.43%, 48.16%, and 45.63%, respectively. Figure 8 It can be seen that the ammonia nitrogen removal rates of permeable bricks prepared with different target porosities, from high to low, are: P=10%, P=15%, P=20%, and P=25%, with average ammonia nitrogen reduction rates of 17.29%, 13.96%, 8.05%, and 7.07%, respectively. Therefore, the optimal target porosity for permeable bricks is 15%.

[0084] Depend on Figure 4 It can be seen that the compressive strength and permeability coefficient of permeable bricks prepared with different fly ash contents vary significantly. As the fly ash content increases, the permeability coefficient of the permeable bricks gradually decreases. Figure 11 It can be seen that the orthophosphate removal rate of permeable bricks prepared with different fly ash admixtures, from high to low, is: C f =20%, C f =15%, C f =10%, C f =5%, with average reduction rates of orthophosphate of 74.46%, 60.06%, 53.48%, and 50.73%, respectively. Figure 12 It can be seen that the ammonia nitrogen removal rate of permeable bricks prepared with different fly ash admixtures, from high to low, is: C f =20%, Cf =15%, C f =10%, C f =5%, with average ammonia nitrogen reduction rates of 21.22%, 15.53%, 13.94%, and 9.16%, respectively. Therefore, the optimal fly ash content is 20%.

[0085] In summary, the active permeable brick prepared in Example 15 exhibits the best performance, with the optimal parameters being: W / C = 0.26, P = 15%, D = 3-6 mm, and C = 15%. f =20%. The active permeable bricks prepared by the method of this invention have high compressive strength, good water permeability, and excellent nitrogen and phosphorus removal performance, which can effectively reduce nitrogen and phosphorus pollutants in water bodies and alleviate the problem of eutrophication in urban rivers and lakes.

[0086] 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 the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing an active permeable brick for reducing nitrogen and phosphorus pollutants in rainwater, characterized in that: Includes the following steps: (1) The limestone is mechanically vibrated and screened to obtain limestone with a particle size of 3-6 mm, and then washed and air-dried. (2) The water-cement ratio was set to 0.26, the target porosity was 15%, the aggregate particle size was 3-6 mm, the fly ash content was 20% of the total cement mass, and the water-reducing agent content was 1% of the water mass. The volumetric method was used to calculate the amount of each material, and the ratio of aggregate, cement, fly ash, water and water-reducing agent was found to be 1731:580:145:151:1.

51. (3) Using limestone as aggregate, weigh limestone, fly ash, silicate cement, water and water-reducing agent, mix and stir evenly to obtain a mixture; (4) The mixture is filled into the mold in layers and shaped. After each layer of mixture is filled, the mold is vibrated at a high frequency and low amplitude. Then, the mixture is tamped evenly with a tamping rod. (5) The molded bricks, together with the mold, are placed in a concrete curing box with a temperature of 20±2℃ and a relative humidity of more than 95% and cured for 1 day. (6) After demolding the bricks in the mold, continue curing for 28 days to obtain the finished active permeable brick.

2. The method for preparing an active permeable brick for reducing nitrogen and phosphorus pollutants in rainwater according to claim 1, characterized in that: In step (2), the fly ash grade is Class II.

3. The method for preparing an active permeable brick for reducing nitrogen and phosphorus pollutants in rainwater according to claim 1, characterized in that: In step (3), the stirring time is 1 minute, until the aggregate surface is completely coated with silicate cement and exhibits a metallic luster.

4. The method for preparing an active permeable brick for reducing nitrogen and phosphorus pollutants in rainwater according to claim 1, characterized in that: In step (4), the mold is vibrated for 10 seconds after each layer of material is filled, and the material is tamped 50 times with a tamping rod.

5. The method for preparing an active permeable brick for reducing nitrogen and phosphorus pollutants in rainwater according to claim 1, characterized in that: In step (6), the bricks in the mold are demolded and then sent into the concrete curing box for curing. After curing, the active permeable brick product is obtained.

6. An active permeable brick for reducing nitrogen and phosphorus pollutants in rainwater, characterized in that: The permeable bricks are prepared by the method described in any one of claims 1 to 5, and the dimensions are 200×100×60mm.

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