Fluidized solidified soil based on waste filter-pressed soil and preparation method thereof

Abstract

The invention discloses flow-state solidified soil based on gravel production waste filter-pressed soil, which is characterized by comprising the following raw materials in parts by weight: 770-900 parts of filter-pressed soil, 160-400 parts of a cement-based curing agent, 100-150 parts of plant ash, 1-2 parts of a soluble strong electrolyte regulator, 1-2 parts of a nonionic dispersant and 500-580 parts of water, and the soluble strong electrolyte regulator is inorganic sodium salt. The flow-state solidified soil disclosed by the invention has good working performance, mechanical property, water stability and the like at the same time of realizing large-mixing-amount resource utilization of the filter pressing soil, and has remarkable economic and environmental benefits; and the related preparation method is relatively simple, relatively low in cost and suitable for popularization and application.

Description

Technical Field

[0001] This invention belongs to the field of building materials and solid waste resource utilization technology, specifically relating to a fluidized solidified soil based on waste filter soil and its preparation method. Background Technology

[0002] In the production of sand and gravel aggregates, the stones need to be repeatedly washed. The resulting slurry is usually treated with flocculants to accelerate the sedimentation of soil particles. The settled slurry is then filtered to form filter soil. Filter soil is often directly stockpiled or landfilled due to its fine particles, high water content, large amount of flocculant, and poor mechanical properties. This not only occupies land resources but also poses environmental risks such as dust pollution and soil erosion. Fluidized solidified soil is a new type of environmentally friendly building material. It is produced by mixing solid waste such as construction waste and waste slurry with a solidifying agent (such as cement, slag, fly ash, etc.) and water to form a highly fluid, pumpable slurry. After pouring and curing, it solidifies into a geotechnical material with good engineering properties. Exploring the application of filter soil in the preparation of fluidized solidified soil could provide a new approach for the resource utilization of sand and gravel waste materials.

[0003] However, filter press soil typically contains a large amount of flocculant (mainly composed of organic matter such as polyacrylamide), and its fine particles result in a high plasticity index. When used to prepare fluidized solidified soil, this can easily lead to problems such as high water consumption, poor fluidity, long setting time, easy cracking, and insufficient strength. Therefore, there is an urgent need for a low-cost, green, and efficient method to realize the resource utilization of waste sand and gravel filter press soil. Summary of the Invention

[0004] The main objective of this invention is to address the current difficulties in the resource utilization of waste filter soil by providing a fluidized solidified soil prepared from waste filter soil, while taking into account the workability, mechanical properties and water stability of the fluidized solidified soil.

[0005] Another objective of this invention is to provide a low-cost, simple, and efficient method for preparing fluidized solidified soil.

[0006] To achieve the objective, the technical solution adopted by this invention is as follows:

[0007] A fluidized solidified soil based on waste filter press soil, comprising the following raw materials and their respective weight proportions: 770-900 parts filter press soil, 160-400 parts cement-based solidifying agent, 100-150 parts wood ash, 1-2 parts soluble strong electrolyte regulator, 1-2 parts nonionic dispersant, and 500-580 parts water; wherein the soluble strong electrolyte regulator is an inorganic sodium salt.

[0008] In the above scheme, the filter soil is heated before use; the heating temperature is 80-85℃ and the time is 3-3.5h.

[0009] In the above scheme, the filter soil is the soil obtained by pressing and filtering the waste slurry generated during the washing process of sand and gravel aggregate production after sedimentation with flocculant. The moisture content is 25-35%. When measuring, the moisture content is calculated and deducted from the total water consumption.

[0010] Furthermore, the particle size of the filter press soil is 2–200 μm; the content of the flocculating component (mainly polyacrylamide) is 1–2 wt%.

[0011] Furthermore, the main chemical components of the filter soil include SiO2, Al2O3, MgO and K2O.

[0012] In the above scheme, the cement-based curing agent includes cement, fly ash and mineral powder.

[0013] Furthermore, the mass ratio of cement, fly ash, and mineral powder in the cement-based curing agent is 80–230:30–80:50–100.

[0014] In the above scheme, the pH value of the wood ash is 11-12, and the loss on ignition is no more than 5.0%.

[0015] Furthermore, the content of calcium oxide (CaO) in the plant ash is 30-35%, and the content of magnesium oxide (MgO) is 5-8%.

[0016] Furthermore, the plant ash is straw plant ash.

[0017] In the above scheme, the soluble strong electrolyte regulator is one or a mixture of two of NaCl and Na2SO4; the present invention introduces a soluble strong electrolyte regulator, utilizing its strong electrolytic effect to make Na... + Cl - and SO4 2- The flocculant preferentially adsorbs (competitively adsorbs) onto the filter press particles, disrupting the adsorption of the flocculant onto the filter press particles. Simultaneously, it can further act on the flocculant components of the heat-treated filter press, compressing the diffused electric double layer around the molecular chains of polyacrylamide and other substances, causing chain coiling, further reducing the adsorption capacity of the corresponding flocculant components, and effectively eliminating the adverse effects of the flocculant components on the application of fine-particle filter presses. In the above scheme, the nonionic dispersant is polyvinylpyrrolidone with a molecular weight of 30,000–50,000.

[0018] The present invention also provides a method for preparing the above-mentioned fluidized solidified soil, comprising the following steps:

[0019] 1) Mix the heat-treated filter soil with wood ash evenly;

[0020] 2) Add a soluble strong electrolyte regulator and some water to the mixture obtained in step 1), and stir.

[0021] 3) Add the remaining water, nonionic dispersant and cement-based curing agent, and stir evenly to obtain the fluidized solidified soil.

[0022] In the above scheme, the stirring time in step 2) is 3 to 5 minutes, and a uniform and fine slurry is formed.

[0023] In the above scheme, in step 2), the added water accounts for 2 / 3 to 3 / 4 of the total water consumption.

[0024] The main principles of this invention include:

[0025] 1) The filter soil contains a large amount of flocculant (mainly polyacrylamide). This invention first heat-treats the filter soil at 80-85℃ to thermally degrade or coil the polyacrylamide molecular chains, destroying their original structure, reducing adsorption sites, and decreasing the flocculation effect on soil particles. Then, a soluble strong electrolyte regulator, NaCl and / or Na2SO4, is introduced for stirring treatment to further compress the diffused double layer around the polyacrylamide molecular chains, causing chain coiling and reducing adsorption capacity. At the same time, it can also destroy the van der Waals forces and hydrogen bonds between it and soil particles, further eliminating the influence of flocculant components. In addition, Na2SO4 can accelerate the hydration of the solidifying agent and improve the early strength of the solidified soil.

[0026] 2) This invention first incorporates wood ash with a pH of 11-12 into the heat-treated filter soil. On the one hand, this adjusts the pH of the filter soil to make it alkaline, increasing the solubility of metal hydroxides in the soil and thus destroying its flocculation structure. On the other hand, the main components of wood ash are calcium oxide (CaO) and magnesium oxide (MgO), which react with water to generate Ca(OH)2 and Mg(OH)2, which can further improve the compactness of the solidified soil. At the same time, it undergoes a secondary hydration reaction with the hydration products of the solidifying agent, further improving the strength of the solidified soil and reducing its shrinkage.

[0027] 3) This invention uses a non-ionic dispersant, which effectively avoids the problem of ionic dispersants being adsorbed by flocculants and thus having poor effects. It can significantly reduce the water consumption of solidified soil, significantly improve the fluidity of solidified soil, and optimize the strength, impermeability and shrinkage properties of concrete.

[0028] Compared with the prior art, the beneficial effects of the present invention include:

[0029] 1) This invention comprehensively treats the waste filter soil generated during the sand and gravel production process, combining heat treatment, strong electrolyte competitive adsorption, and non-ionic dispersant strong dispersion to significantly eliminate the adverse effects of high flocculant content in the soil particles of waste filter soil, and promotes the large-scale resource utilization of waste filter soil in fluidized solidified soil.

[0030] 2) This invention can effectively solve the problems of high water consumption, poor fluidity, long setting time, easy cracking and insufficient strength when preparing fluidized solidified soil from filter press soil. It takes into account the good workability, mechanical properties and water stability of fluidized solidified soil, and has great environmental and economic benefits.

[0031] 3) The present invention has low cost, simple preparation method and low equipment requirements, and is suitable for widespread application. Detailed Implementation

[0032] The technical solutions adopted in this invention are described in detail below through specific implementation examples. These descriptions are merely a part of the invention and do not represent all embodiments. Unless otherwise specified, the experimental methods used in this invention are conventional methods, and the instruments and equipment used are commercial products in this technical field.

[0033] In the following examples, the filter soil used was waste filter soil generated during the production of sand and gravel in a certain company. The filter soil contained 65wt% SiO2, 20wt% Al2O3, and 12wt% MgO and K2O. The particle size was 2-150μm, and the flocculant (mainly polyacrylamide) content was 1.5wt%.

[0034] The wood ash used is wood ash obtained from burning straw, which contains 33 wt% calcium oxide (CaO) and 7 wt% magnesium oxide (MgO).

[0035] The raw materials and their quantities used in the fluidized solidified soil based on waste filter soil from sand and gravel production described in Examples 1 to 6 are shown in Table 1.

[0036] Table 1 shows the mix proportions (parts by weight) of the fluidized solidified soil described in Examples 1-6.

[0037]

[0038]

[0039] Example 1

[0040] A fluidized solidified soil based on waste filter press soil, the raw material ratio of which is shown in Table 1; the specific preparation method includes the following steps:

[0041] 1) Heat the filter soil at 82℃ for 3.5 hours;

[0042] 2) Mix the heat-treated filter soil with wood ash for 4 minutes to form a uniform and fine flowing slurry;

[0043] 3) Add the regulator and 3 / 4 of the water to the resulting mixture and stir until well combined;

[0044] 4) Add the remaining water, dispersant (polyvinylpyrrolidone, molecular weight 50,000) and cement-based curing agent, and stir evenly to obtain the fluidized solidified soil.

[0045] Example 2

[0046] A fluidized solidified soil based on waste filter press soil, the raw material ratio of which is shown in Table 1; the specific preparation method includes the following steps:

[0047] 1) Heat the filter soil at 85℃ for 3.3 hours;

[0048] 2) Mix the heat-treated filter soil with wood ash for 3.5 minutes to form a uniform and fine flowing slurry;

[0049] 3) Add the regulator and 3 / 4 of the water to the resulting mixture and stir until well combined;

[0050] 4) Add the remaining water, dispersant (polyvinylpyrrolidone, molecular weight 40000) and cement-based curing agent, and stir evenly to obtain the fluidized solidified soil.

[0051] Example 3

[0052] A fluidized solidified soil based on waste filter press soil, the raw material ratio of which is shown in Table 1; the specific preparation method includes the following steps:

[0053] 1) Heat the filter soil at 82℃ for 3.2 hours;

[0054] 2) Mix the heat-treated filter soil with wood ash for 3 minutes to form a uniform and fine flowing slurry;

[0055] 3) Add the regulator and 3 / 4 of the water to the resulting mixture and stir until well combined;

[0056] 4) Add the remaining water, dispersant (polyvinylpyrrolidone, molecular weight 40000) and cement-based curing agent, and stir evenly to obtain the fluidized solidified soil.

[0057] Example 4

[0058] A fluidized solidified soil based on waste filter press soil, the raw material ratio of which is shown in Table 1; the specific preparation method includes the following steps:

[0059] 1) Heat-treat the filter soil at 82℃ for 3.1 hours;

[0060] 2) Mix the heat-treated filter soil with wood ash for 5 minutes to form a uniform and fine flowing slurry;

[0061] 3) Add the regulator and 3 / 4 of the water to the resulting mixture and stir until well combined;

[0062] 4) Add the remaining water, dispersant (polyvinylpyrrolidone, molecular weight 30000) and cement-based curing agent, and stir evenly to obtain the fluidized solidified soil.

[0063] Example 5

[0064] A fluidized solidified soil based on waste filter press soil, the raw material ratio of which is shown in Table 1; the specific preparation method includes the following steps:

[0065] 1) Heat the filter soil at 82℃ for 3.0h;

[0066] 2) Mix the heat-treated filter soil with wood ash for 5 minutes to form a uniform and fine flowing slurry;

[0067] 3) Add the regulator and 3 / 4 of the water to the resulting mixture and stir until well combined;

[0068] 4) Add the remaining water, dispersant (polyvinylpyrrolidone, molecular weight 30000) and cement-based curing agent, and stir evenly to obtain the fluidized solidified soil.

[0069] Example 6

[0070] A fluidized solidified soil based on waste filter press soil, the raw material ratio of which is shown in Table 1; the specific preparation method includes the following steps:

[0071] 1) Heat the filter soil at 82℃ for 3.0h;

[0072] 2) Mix the heat-treated filter soil with wood ash for 4 minutes to form a uniform and fine flowing slurry;

[0073] 3) Add the regulator and 3 / 4 of the water to the resulting mixture and stir until well combined;

[0074] 4) Add the remaining water, dispersant (polyvinylpyrrolidone, molecular weight 50,000) and cement-based curing agent, and stir evenly to obtain the fluidized solidified soil.

[0075] Comparative Example 1

[0076] A fluidized solidified soil based on waste filter press soil is prepared in a manner similar to that of Example 1, except that the heat treatment described in step 1) is not performed.

[0077] Comparative Example 2

[0078] A fluidized solidified soil based on waste filter press soil is prepared in a manner similar to that of Example 2, except that wood ash is replaced with fly ash.

[0079] Comparative Example 3

[0080] A fluidized solidified soil based on waste filter press soil is prepared in a manner similar to that of Example 3, except that CaCl2 is used as a modifier instead of Na2SO4 by mass.

[0081] Comparative Example 4

[0082] A fluidized solidified soil based on waste filter press soil is prepared in a manner similar to that of Example 4, except that sodium hexametaphosphate is used as a dispersant instead of polyvinylpyrrolidone by mass.

[0083] Comparative Example 5

[0084] A fluidized solidified soil based on waste filter press soil is prepared in a manner similar to that of Example 5, except that the heat treatment temperature of the filter press soil is 70°C.

[0085] Comparative Example 6

[0086] A fluidized solidified soil based on waste filter press soil is prepared in a manner similar to that of Example 6, except that the pre-mixing treatment of the filter press soil obtained by heat treatment in step 2) with wood ash is not performed. Instead, the filter press soil obtained by heat treatment is directly mixed with wood ash, regulator and water until homogeneous.

[0087] According to DBJ51-T188-2022 "Technical Standard for Engineering Application of Premixed Flowable Solidified Soil", the above-mentioned embodiments and comparative examples were tested, mainly including flow spread, 7d / 28d compressive strength and water stability coefficient. The test results are shown in Table 2.

[0088] Table 2. Performance test results of fluidized solidified soil

[0089]

[0090] As can be seen from Examples 1 to 6, the prepared fluidized solidified soil has excellent workability, mechanical properties and water stability; it can realize the high-value-added resource utilization of waste filter soil from sand and gravel production in the field of fluidized solidified soil.

[0091] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It should be understood that the above are merely some embodiments of the present invention and are not intended to limit the invention. Therefore, any changes and improvements to the above embodiments should be included within the scope of protection of the claims of this invention.

Claims

1. A fluidized solidified soil based on waste filter press soil, characterized in that, The raw materials and their respective weight percentages include: 770-900 parts of filter soil, 160-400 parts of cement-based curing agent, 100-150 parts of wood ash, 1-2 parts of soluble strong electrolyte regulator, 1-2 parts of nonionic dispersant, and 500-580 parts of water; the soluble strong electrolyte regulator is an inorganic sodium salt.

2. The fluidized solidified soil according to claim 1, characterized in that, The filter soil is heated before use; the heating temperature is 80-85℃ and the time is 3-3.5h.

3. The fluidized solidified soil according to claim 1, characterized in that, The filter soil has a particle size of 2–200 μm, a moisture content of 25–35%, and a flocculation component content of 1–2 wt%.

4. The fluidized solidified soil according to claim 1, characterized in that, The cement-based curing agent comprises cement, fly ash, and mineral powder.

5. The fluidized solidified soil according to claim 4, characterized in that, The mass ratio of cement, fly ash and mineral powder in the cement-based curing agent is 80-230:30-80:50-100.

6. The fluidized solidified soil according to claim 1, characterized in that, The plant ash has a pH value of 11-12 and a loss on ignition of no more than 5.0%; the calcium oxide content is 30-35%, and the magnesium oxide content is 5-8%.

7. The fluidized solidified soil according to claim 1, characterized in that, The soluble strong electrolyte regulator is one or a mixture of two of NaCl and Na2SO4.

8. The fluidized solidified soil according to claim 1, characterized in that, The nonionic dispersant is polyvinylpyrrolidone with a molecular weight of 30,000 to 50,000.

9. The method for preparing the fluidized solidified soil according to any one of claims 1 to 8, characterized in that, Includes the following steps: 1) Mix the heat-treated filter soil with wood ash evenly; 2) Add a soluble strong electrolyte regulator and some water to the mixture obtained in step 1), and stir. 3) Add the remaining water, nonionic dispersant and cement-based curing agent, and stir evenly to obtain the fluidized solidified soil.

10. The preparation method according to claim 9, characterized in that, In step 2), the added water accounts for 2 / 3 to 3 / 4 of the total water consumption.

Images