Method for building lawn by using modified sludge slurry and recycled aggregate

Abstract

The invention relates to the field of comprehensive utilization of waste resources, and particularly discloses a method for building a lawn by using modified sludge slurry and recycled aggregate. The method comprises the following steps: adding a sludge dispersing agent and a curing agent into sludge, uniformly stirring, adding mixed sowing lawn grass seeds, and stirring and dispersing to obtain modified sludge slurry; the method comprises the following steps: crushing and screening the building demolition garbage to obtain recycled aggregate; performing on-site lawn construction by using the modified sludge slurry and the recycled aggregate; performing lawn maintenance. The method can absorb the sludge in a large capacity, and the sludge dispersing agent is matched with the curing agent to cure harmful ions in the sludge and prevent the harmful ions from being absorbed and migrated by plants; after the modified sludge slurry and the recycled aggregate are combined for construction and maintenance, a stable lawn with high bearing capacity can be formed, the alkalinity of the system is low, and grass plants are allowed to grow out from the interior.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of comprehensive utilization of waste resources, and more particularly to a method for building a lawn using modified sludge and recycled aggregates. BACKGROUND

[0002] In recent years, with the vigorous promotion of dredging and desilting of rivers, lakes and reservoirs and water body restoration work, a large amount of sludge has been produced. These sludges have characteristics such as high water content, high porosity, rich in organic matter, low permeability, and large compressibility. If these sludges can be effectively utilized, not only can environmental pollution be reduced, but also resource recycling can be achieved, which has significant environmental and economic value. At the same time, the amount of construction demolition waste is also increasing, and how to reasonably dispose of these wastes and make them resourceful is also an important problem currently faced.

[0003] In the aspect of sludge treatment, there are various common methods in the past. One is to directly landfill the sludge after simple pretreatment, which is simple and easy to implement, has large sludge disposal capacity, and low cost. A large number of researches and practices have carried out the application of sludge in the agricultural field, such as composting or preparing plant soil, because the river and lake sludge is rich in organic matter and nutrient salt, which is a good fertilizer for agricultural or planting. In addition, the sludge after solidification is also used for backfilling, road construction and foundation, which is a method of sludge resource utilization.

[0004] However, the existing sludge treatment and utilization methods have obvious defects. Directly landfilling sludge will bring serious environmental and geological safety hazards. The application of sludge in the agricultural field is affected by industrial wastewater, agricultural non-point source pollution and water biological corruption, and the river bottom mud often contains heavy metals and organic pollutants, which restricts its application. And the sludge after solidification generally needs to add more costly solidifying agent, and the commonly used solidifying agent is alkaline, which can easily cause the surrounding soil to be metamorphic saline-alkali, affecting the growth of surrounding plants. SUMMARY

[0005] In order to solve the above problems, the present application provides a method for building a lawn using modified sludge and recycled aggregates.

[0006] The technical scheme adopted by the present application is as follows: A method for building a lawn using modified sludge and recycled aggregates, comprising: (1) adding a sludge dispersing agent and a solidifying agent to sludge with a water content of 60-80%, stirring uniformly, adding mixed lawn grass seeds, stirring and dispersing to obtain modified sludge with a water content of 45-55%; (2) crushing and screening the construction demolition waste to obtain recycled aggregates; (3) using the modified sludge and the recycled aggregates for on-site lawn construction; (4) Perform lawn maintenance.

[0007] By adopting the technical scheme, the sludge can be accommodated in large capacity, the sludge dispersing agent and the adding amount can better disperse the sludge, the harmful ions in the solidified sludge are combined with the solidifying agent to avoid being absorbed and migrated by plants, the modified sludge slurry is combined with the recycled aggregate to form a relatively stable and high-load-bearing lawn after construction and maintenance, the system has low alkalinity, the grass plants can grow from the inside, the process is simple, the cost is low, and the practicality is high.

[0008] Further, the adding amount of the sludge dispersing agent is 2-3wt% of the mass of the sludge. The sludge dispersing agent is a mixture of a naphthalene-based water reducing agent, sodium hexametaphosphate, a tartrate, and a polyacrylate.

[0009] By adopting the technical scheme, the sludge dispersing agent mixed by the naphthalene-based water reducing agent, the sodium hexametaphosphate, the tartrate, and the polyacrylate is added to the sludge with a water content of 60-80% and accounts for 2-3wt% of the mass of the sludge, the fluidity and dispersibility of the sludge can be effectively improved, the solidifying agent added subsequently can be more uniformly mixed with the sludge, and thus the solidification effect of the sludge is improved; meanwhile, the mixed grass seeds can be uniformly dispersed in the sludge, good conditions are created for the germination and growth of the grass seeds, the water content of the modified sludge slurry is reduced to 45-55%, and the requirements of subsequent lawn construction are met.

[0010] Further, in terms of mass fraction, the naphthalene-based water reducing agent accounts for 50-70 parts, the sodium hexametaphosphate accounts for 15-25 parts, the tartrate accounts for 5-10 parts, and the polyacrylate accounts for 5-15 parts.

[0011] Preferably, the naphthalene-based water reducing agent is a naphthalenesulfonate formaldehyde condensate, which is the main force of the dispersion system, provides main steric hindrance and electrostatic repulsion, efficiently disperses sludge particles, reduces the viscosity of the system, and improves the fluidity.

[0012] Preferably, the sodium hexametaphosphate, as an inorganic dispersing agent and a chelating agent, can effectively disperse clay particles and chelate multivalent metal ions (such as Ca 2+ ,Mg 2+ ,Fe 3+ ) in the sludge to prevent these ions from flocculating sludge particles.

[0013] Preferably, the tartrate is sodium tartrate or potassium tartrate, which mainly acts as a chelating agent / complexing agent to assist the sodium hexametaphosphate in further stabilizing the multivalent metal ions.

[0014] Preferably, the polyacrylate is sodium polyacrylate or potassium polyacrylate with a molecular weight of 2000-5000 Da, which helps to maintain the dispersion stability of the system under different conditions.

[0015] Further, the adding amount of the above-mentioned solidifying agent is 35-45wt% of the mass of the silt, and the solidifying agent comprises lithium slag powder, granulated blast furnace slag powder, steel slag powder and low-alkali sulphoaluminate cement.

[0016] Further, in the solidifying agent, the lithium slag powder is 40-60 parts by mass, the granulated blast furnace slag powder is 25-35 parts by mass, the steel slag powder is 5-15 parts by mass, and the low-alkali sulphoaluminate cement is 5-15 parts by mass.

[0017] By using the above technical solution, the solidifying agent containing lithium slag powder, granulated blast furnace slag powder, steel slag powder and low-alkali sulphoaluminate cement accounts for 35-45wt% of the mass of the silt. The low-alkali sulphoaluminate cement has low alkalinity, does not affect the germination and growth of the internal grass seeds while solidifying the lawn, and can provide the grass seeds with trace elements required for growth. The lithium slag powder, granulated blast furnace slag powder and steel slag powder can hydrate and solidify the silt, remove harmful ions in the solidified silt to avoid being absorbed and migrated by plants, and together with the low-alkali sulphoaluminate cement, form a certain strength, which allows the grass plants to grow from the inside and can accommodate a large amount of silt.

[0018] Preferably, the lithium slag powder, granulated blast furnace slag powder, steel slag powder and low-alkali sulphoaluminate cement meet the requirements of YB / T4230 Lithium Slag Powder for Use in Cement and Concrete, GB / T 18046 Granulated Blast Furnace Slag Powder for Use in Cement, Mortar and Concrete, GB / T 20491 Steel Slag Powder for Use in Cement and Concrete, and GB / T 20472 Sulphoaluminate Cement, respectively.

[0019] Further, the preparation method of the modified silt slurry comprises: After the silt produced by dredging a river channel, a lake or a reservoir is separated from sand and stone, silt with a water content of 60-80% is obtained and is transported to a high-speed dispersing agent for stirring; The silt dispersing agent and the solidifying agent are sequentially added during the stirring, and the stirring is continued; The mixed lawn grass seeds are added during the stirring, the adding amount of the mixed lawn grass seeds is 0.5-1.5wt% of the total mass of the silt, silt dispersing agent and solidifying agent, and after uniform stirring and dispersion, a modified silt slurry with a water content of 45-55% is obtained.

[0020] By adopting the technical scheme, the separated silt is stirred by the high-speed dispersion machine, and the silt dispersing agent and the solidifying agent are added in sequence, so that the components can be fully mixed, and the uniformity of the modified silt slurry can be effectively improved; meanwhile, the turf grass seeds are added in a specific proportion, so that the turf grass seeds can be uniformly distributed in the modified silt slurry, which is beneficial to the germination and growth of the turf grass seeds, and the amount of the turf grass seeds can be accurately controlled; and the water content of the modified silt slurry is controlled in a suitable range through stirring, so that the solidification requirement is met, and a suitable humidity environment for the growth of the turf grass seeds is provided.

[0021] Further, the recycled aggregate is a single-grain recycled aggregate with a size of 30-40 mm.

[0022] By adopting the technical scheme, the single-grain recycled aggregate with a size of 30-40 mm can provide a high packing void ratio and abundant surface pore structure, and provide sites and space for root growth, and has a certain bearing capacity, which is beneficial to forming a relatively stable and high-bearing-capacity lawn.

[0023] Further, the method for constructing the lawn on site comprises the following steps: After the hardening base layer floating dust and sundries are cleaned, the modified silt slurry is sprayed to wet the hardening base layer; The recycled aggregate is conveyed to a work site for paving, the paving layer is wetted by spraying water, and the modified silt slurry is injected to the paving site until the modified silt slurry seeps into the packing voids of the recycled aggregate and covers the paving layer of the recycled aggregate by self-leveling; The above steps are repeated for 1-5 times until the set lawn thickness is reached.

[0024] Further, the method for maintaining the lawn comprises the following steps: The surface of the paving layer is covered with a plastic film, and after the turf grass seeds germinate and grow out, the plastic film is removed, and the surface of the lawn is irrigated with water until the lawn is formed.

[0025] Further, the core drilling sampling compressive strength of the lawn is 0.2-0.3 MPa.

[0026] By adopting the technical scheme, the modified silt slurry is first sprayed to wet the hardening base layer, which is beneficial to subsequent construction; the recycled aggregate is paved and wetted by spraying water, and then the modified silt slurry is injected, so that the modified silt slurry can seep into the packing voids of the recycled aggregate and cover by self-leveling, thereby ensuring the full combination of the two; the operation is repeated until the set lawn thickness is reached, so that the lawn thickness can be accurately controlled, and the on-site construction of the lawn is efficiently and accurately completed. Through the film covering and maintenance, a suitable germination and growth environment can be provided for the turf grass seeds, so that the turf grass seeds can germinate and grow out smoothly, and finally form a lawn, and the lawn has a certain compressive strength, which meets the requirements of stability and bearing capacity of the lawn in actual use, thereby forming a relatively stable lawn structure.

[0027] In summary, the application has the following beneficial effects: 1. The application can accommodate a large amount of sludge, find a suitable resource utilization scheme for dredging sludge, and utilize recycled aggregates to process construction demolition waste, achieving resource recycling; 2. The application has low alkalinity, can solidify harmful ions in the sludge, avoid being absorbed and migrated by plants, and does not affect the germination and growth of the internal grass seeds, and can also provide trace elements required for the growth of the grass seeds; 3. The application has strong bearing capacity, high void ratio, rough and porous particle surface, can provide sites and space for root growth, and the formed lawn has a certain bearing capacity; 4. The application directly uses sludge, does not need to be composted for a long time or prepared into plant soil, has simple process, low cost, and strong practicability. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a flowchart of the method provided by the embodiment 1 of the application. DETAILED DESCRIPTION

[0029] The embodiments of the application will be described in detail below with reference to the examples, but those skilled in the art will understand that the following examples are only used to illustrate the application, and should not be regarded as limiting the scope of the application. The specific conditions not mentioned in the examples are carried out according to the conventional conditions or the conditions recommended by the manufacturer, and the reagents or instruments not mentioned by the manufacturer are conventional products that can be purchased on the market.

[0030] The specific embodiments of the application will be described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the application, and are not used to limit the application. EMBODIMENT

[0031] Embodiment 1 The embodiment provides a method for building a lawn using sludge and recycled aggregates, specifically comprising the following steps: 1. Preparation of modified sludge The sludge produced by dredging of a river, lake or reservoir is separated from sand and stone, and has a water content of 70%, and is transported to a high-speed dispersing machine for high-speed stirring. A sludge dispersing agent (as shown in Table 1) accounting for 2.5% of the mass of the sludge is added to the high-speed dispersing machine, and the stirring is continued. A solidifying agent (as shown in Table 2) accounting for 40% of the mass of the sludge is added to the high-speed dispersing machine, and the stirring is continued. A mixed lawn grass seed accounting for 1% of the total mass of the above-mentioned materials is added to the high-speed dispersing machine, and the stirring is continued. The high-speed stirring and dispersing obtain a modified sludge with a water content of 50%.

[0032] 2. Recycled aggregate processing The construction demolition waste is transported to a treatment site, and large-size steel bars are separated by a mechanical hammer crusher. The crushed pieces are loaded into a secondary crusher for secondary crushing, and sieved to obtain 30-40mm single-size recycled aggregate.

[0033] 3. On-site lawn construction Hardened base soil and sundries are cleaned; modified slurry is sprayed to wet the hardened base; recycled aggregate is transported to a paving site; the paved layer is watered; modified slurry is injected to the paving site until the modified slurry seeps into the voids of the recycled aggregate and covers the recycled aggregate paving layer; the above steps are repeated until the set lawn thickness is reached.

[0034] 4. Lawn maintenance The surface of the paving layer is covered with a plastic film until the grass seeds germinate and grow out, and then the plastic film is removed, and the lawn surface is watered until the lawn is formed.

[0035] Example 2-3 The difference between this group of examples and Example 1 is that the components and proportions of the sludge dispersant are different, as shown in Table 1.

[0036] Table 1. Ingredients Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Naphthalene-based water reducer 60 70 50 60 60 Sodium hexametaphosphate 20 15 25 30 / Potassium tartrate 10 10 10 / 30 Sodium polyacrylate 10 5 15 10 10 Example 4-5 The difference between this group of examples and Example 1 is that the components and proportions of the curing agent are different, as shown in Table 2.

[0037] Table 2. Example 6 The difference between this example and Example 1 is that the amount of sludge dispersant is 3wt%, and the amount of curing agent is 45wt%.

[0038] Example 7 The difference between this example and Example 1 is that the amount of sludge dispersant is 2wt%, and the amount of curing agent is 35wt%.

[0039] Comparative Example Comparative Example 1-2 The difference between this comparative example and Example 1 is that the components and proportions of the sludge dispersant are different, as shown in Table 1.

[0040] Comparative Example 3-4 The difference between this comparative example and Example 1 is that the components and proportions of the curing agent are different, as shown in Table 2.

[0041] Comparative Example 5 The difference between this comparative example and Example 1 is that the low-alkali sulfoaluminate cement in the curing agent is replaced with an equal amount of ordinary portland cement.

[0042] Performance test Detection method / test method The lawns built by the methods provided in the above examples and comparative examples were detected, lawn maintenance was carried out under the same conditions, and the germination rate of the lawn and the compressive strength of the lawn were measured, and the results are shown in Table 3.

[0043] Table 3. Lawn sample Germination rate (%) Compressive strength (Mpa) Example 1 89.6 0.30 Example 2 84.3 0.25 Example 3 85.1 0.27 Example 4 84.9 0.26 Example 5 86.4 0.25 Example 6 87.3 0.28 Example 7 84.2 0.24 Comparative Example 1 65.4 0.23 Comparative Example 2 61.3 0.24 Comparative Example 3 52.6 0.25 Comparative Example 4 56.2 0.17 Comparative Example 5 51.5 0.23 As can be seen from Table 3: The lawn provided in examples 1-7 has a germination rate of the grass seed of more than 84%, and the germination rate of the excellent one can reach 89%; at the same time, the compressive strength is basically maintained at 0.24-0.30 Mpa. Thus, it is illustrated that the lawn building method provided in the present application can effectively solidify the harmful ions in the silt, and at the same time, the lawn has a certain compressive strength, and can form a stable lawn structure.

[0044] As can be seen from examples 1 and comparative examples 1-2, the tartrate and hexametaphosphate in the silt dispersing agent are crucial to the germination rate of the final lawn. This is mainly because the hexametaphosphate can effectively disperse the clay particles and chelate the multivalent metal ions (such as Ca 2+ ,Mg 2+ ,Fe 3+ ) in the silt to further promote the solidification of the subsequent metal ions; and the tartrate can assist the hexametaphosphate to further stabilize the multivalent metal ions and strengthen the solidification effect. The tartrate and hexametaphosphate synergistically improve the germination rate of the lawn.

[0045] As can be seen from examples 1 and comparative examples 3-5, the selection of the components in the solidifying agent is crucial to the germination rate and compressive strength of the lawn. In comparative example 3, the granulated blast furnace slag powder is lacking, although the compressive strength is maintained to a certain extent by increasing the amount of cement, but the granulated blast furnace slag powder is the main gel material and harmful ion solidification carrier, and in the absence of it, it is not conducive to the germination of the seeds. In comparative example 4, the steel slag powder is lacking, and the germination rate and compressive strength have decreased to different degrees. This is because the iron phase minerals contained in the steel slag powder have a good fixation effect on specific heavy metals (such as forming chromite phase); and can be hydrated to provide late strength under the excitation of lithium slag powder. In comparative example 5, the ordinary portland cement (pH is usually greater than 11.5) is used to replace the low-alkali sulfoaluminate cement, resulting in a high alkalinity of the whole system, which is not conducive to the germination of the grass seeds.

[0046] The specific embodiments are only an explanation of the present application, and are not a limitation of the present application, and those skilled in the art can make modifications to the embodiments without creative contribution after reading the present specification, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A method for constructing lawns using modified sludge slurry and recycled aggregate, characterized in that, It includes: (1) Add sludge dispersant and solidifying agent to sludge with a water content of 60-80%, stir evenly, add mixed turfgrass seeds, stir and disperse to obtain modified sludge slurry with a water content of 45-55%. (2) After crushing and screening the construction demolition waste, recycled aggregate is obtained; (3) Use the modified sludge slurry and the recycled aggregate for on-site lawn construction; (4) Carry out lawn health care.

2. The method for constructing lawns using modified sludge slurry and recycled aggregate according to claim 1, characterized in that, The amount of the sludge dispersant added is 2-3 wt% of the mass of the sludge; The sludge dispersant is a mixture of naphthalene-based water-reducing agent, sodium hexametaphosphate, tartrate, and polyacrylate.

3. The method for constructing lawns using modified sludge slurry and recycled aggregate according to claim 2, characterized in that, By weight, the sludge dispersant contains 50-70 parts of naphthalene-based water-reducing agent, 15-25 parts of sodium hexametaphosphate, 5-10 parts of tartrate, and 5-15 parts of polyacrylate.

4. The method for constructing a lawn using modified sludge slurry and recycled aggregate according to claim 1, characterized in that, The amount of the curing agent added is 35-45 wt% of the mass of the sludge, and the curing agent includes lithium slag powder, granulated blast furnace slag powder, steel slag powder, and low-alkali sulfoaluminate cement.

5. The method for constructing a lawn using modified sludge slurry and recycled aggregate according to claim 4, characterized in that, By weight, the curing agent comprises 40-60 parts lithium slag powder, 25-35 parts granulated blast furnace slag powder, 5-15 parts steel slag powder, and 5-15 parts low-alkali sulfoaluminate cement.

6. The method for constructing a lawn using modified sludge slurry and recycled aggregate according to claim 1, characterized in that, The method for preparing the modified sludge slurry includes: After separating the sand and stones from the silt produced by dredging rivers, lakes or reservoirs, silt with a water content of 60-80% is obtained and transported to a high-speed dispersant for mixing. During the stirring process, the sludge dispersant and the solidifying agent are added sequentially, and stirring continues; During the mixing process, mixed turfgrass seeds are added. The amount of mixed turfgrass seeds added is 0.5-1.5 wt% of the total mass of silt, silt dispersant and curing agent. After stirring and dispersing evenly, a modified silt slurry with a water content of 45-55% is obtained.

7. The method for constructing a lawn using modified sludge slurry and recycled aggregate according to claim 1, characterized in that, The recycled aggregate is a single-size recycled aggregate of 30-40mm.

8. The method for constructing a lawn using modified sludge slurry and recycled aggregate according to any one of claims 1-7, characterized in that, The method for on-site lawn construction includes: After cleaning the loose soil and debris from the hardened base layer, spray the modified sludge slurry to moisten the hardened base layer; The recycled aggregate is transported to the work site for paving. The paving layer is moistened with water, and the modified sludge slurry is sprayed onto the paving site until the modified sludge slurry seeps into the voids of the recycled aggregate and self-levels and covers the recycled aggregate paving layer. Repeat steps 1-5 times until the desired lawn thickness is achieved.

9. The method for constructing a lawn using modified sludge slurry and recycled aggregate according to claim 8, characterized in that, The methods for maintaining lawn health include: Cover the surface of the paving layer with plastic film until the grass seeds germinate and grow. Then remove the plastic film and water the lawn surface until a lawn is formed.

10. The method for constructing a lawn using modified sludge slurry and recycled aggregate according to claim 8, characterized in that, The compressive strength of the lawn, as determined by core drilling, is 0.2-0.3 MPa.

Images