High-efficiency embankment filling soil modifier based on solid waste synergy as well as preparation method and application of high-efficiency embankment filling soil modifier

Abstract

The invention provides an efficient embankment filling soil modifier based on solid waste synergy as well as a preparation method and application thereof, and relates to the field of sludge curing agents. The solid waste synergistic modifier is prepared from the following raw materials in parts by mass: 4 to 5 parts of coal gangue aggregate, 8 to 12 parts of steel slag micro powder, 1.5 to 2 parts of desulfurized gypsum, 0.2 to 0.4 part of polymer reinforced fiber and 2 to 4 parts of Portland cement. According to the obtained solid waste synergistic modifier, the unconfined compressive strength and stability of the solidified soil body are effectively improved, a large amount of spoil excavated in the engineering implementation process is effectively solved, waste recycling is achieved, and environmental protection and energy saving are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sludge solidification agent, and particularly relates to a high-efficiency embankment filling soil modifier based on solid waste cooperation as well as a preparation method and application thereof. BACKGROUND

[0002] In water conservancy, transportation, civil engineering, municipal engineering and other projects, the problem of sludge soft foundation is often encountered. The sludge has the characteristics of high water content, small permeability coefficient, large compressibility and low shear strength, which leads to low bearing capacity of the foundation, easy to produce large settlement and uneven settlement, and brings many difficulties to engineering construction. For example, in the coastal areas, middle and lower reaches of rivers or near lake areas in China, there are a large amount of sludge soft soil, which adds hidden troubles such as roadbed settlement to road construction and other projects.

[0003] Traditional methods such as soil filling and reinforcement, soil replacement cushion and the like have problems such as high cost, long construction period, large demand for earthwork and stone, and are difficult to meet the engineering requirements. Therefore, an efficient and economical method is needed to deal with the sludge soft foundation, and the sludge solidification agent technology emerges as the times require.

[0004] Under the background of advocating green and sustainable development, resource recycling is highly valued. The sludge solidification agent technology can convert the sludge, which is originally regarded as waste, into a usable resource. The solidified sludge can be used in land backfilling, road construction and other fields, realizing waste recycling. Traditional road construction methods not only consume a large amount of resources, pay a large amount of material and transportation fees, but also cause great damage to the environment. How to utilize the existing original soil and effectively improve the unconfined compressive strength and plate performance of the original soil is the technical research direction to solve the road construction problem.

[0005] The Chinese patent application with publication number CN118930197A discloses a sludge solidification agent and a preparation method and application thereof. The raw materials include ordinary Portland cement 90-92 parts, aluminate cement 2-4 parts, starch-acrylonitrile grafted starch 2-4 parts, sucrose 0.03-0.05 parts and sodium silicate 0.05-0.1 parts. However, the addition amount of the cement material for sludge consolidation is large, the cost is high, and the compressive strength of the solidified sludge is only 1.4-1.8 / Mpa, which is poor, so further improvement is needed. SUMMARY

[0006] The technical problem to be solved by the present application is how to solve the problems of high cost and poor performance of the existing sludge solidification agent.

[0007] The present application solves the above technical problems by the following technical means:

[0008] One of the technical solutions of the present application is a solid waste synergistic modifier, according to the mass fraction, the raw materials include: coal gangue aggregate 4-5 parts, steel slag powder 8-12 parts, desulfurization gypsum 1.5-2 parts, polymer reinforcing fiber 0.2-0.4 parts, and Portland cement 2-4 parts.

[0009] Preferably, the raw materials include: coal gangue aggregate 4.3-4.8 parts, steel slag powder 10-11 parts, desulfurization gypsum 1.8-2 parts, polymer reinforcing fiber 0.3-0.4 parts, and Portland cement 2.5-3.5 parts.

[0010] Preferably, the coal gangue aggregate is an angular particle with a particle size of 0.5-2 mm.

[0011] Preferably, the polymer reinforcing fiber is a polypropylene fiber with a length of 10-15 mm, and further preferably 12 mm.

[0012] The second technical solution of the present application is a preparation method of the above-mentioned solid waste synergistic modifier, which comprises the following steps: mixing the raw materials uniformly according to the above-mentioned mass fraction.

[0013] The third technical solution of the present application is the application of the above-mentioned solid waste synergistic modifier in solidifying waste soil or sludge. After mixing the above-mentioned solid waste synergistic modifier with waste soil or sludge, stirring, and compaction, the solidified soil is obtained.

[0014] Preferably, the mixing amount of the solid waste synergistic modifier is 15%-20% of the total mass of the waste soil or sludge.

[0015] Preferably, the water content of the waste soil or sludge is 30-40%, and further preferably 35%.

[0016] Preferably, the stirring is rotary tillage mixing for 5-7 times.

[0017] Preferably, the compaction method is layering and rolling, and the compaction degree is not less than 0.96.

[0018] The roles of each raw material component in the solid waste synergistic modifier in the sludge solidification process are as follows:

[0019] The steel slag powder provides a Ca(OH)2 alkaline excitation environment to generate C-S-H gel, increase the internal friction angle, ensure long-term cementing activity, and reduce the cement dosage.

[0020] The desulfurization gypsum introduces SO42- to generate ettringite (AFt), accelerates ettringite nucleation, enhances the skeleton occlusion force, and solves the problem of insufficient cementing.

[0021] The polymer reinforcing fiber forms a three-dimensional reinforcing network, improves the toughness of the soil body, and enhances the interface bonding.

[0022] Silicate cement, solve the short board of early strength.

[0023] The beneficial effects of the present application are:

[0024] 1. The present application proposes a high-efficiency embankment filling soil modifier based on solid waste cooperation, which can cooperatively improve the shear strength index of soil, control the drying shrinkage rate, ensure long-term water stability, and is low in cost, environmentally friendly, excellent in performance, and solves the problem of a large amount of excavated soil in the engineering implementation process, so that it can be utilized and filled in embankment, solving the problem of large-scale construction in engineering, which can be mixed on site.

[0025] 2. The solid waste cooperative modifier improves the strength of the solidified soil under external load, i.e., the improvement of unconfined compressive strength; on the other hand, it reduces the void ratio of the solidified soil to some extent, so that the soil minerals and cementitious components are combined more closely.

[0026] 3. The solid waste cooperative modifier has better modification effect on silt than cement and some commercially available solidifying agents. On the one hand, the solidifying agent can play a role in densifying the structure of the solidified soil, and on the other hand, its components can stimulate the depolymerization of clay substances. The components of the solidifying agent directly react with silt soil, the layered clay minerals are depolymerized into more active sheet structures, and the solidifying agent and clay form a more compact cementitious contact. With the increase of the solidifying agent content, the cementitious structure formed is more compact, and the water erosion resistance is enhanced. With the increase of the solidifying agent content, the surface of the solidified soil is smoother, and the erosion resistance is stronger.

[0027] 4. The solid waste cooperative modifier based on solid waste cooperation has a solid waste content of ≥90%, and the cost is reduced by 50% compared with cement and other solidification. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The unconfined compressive strength test process diagram of the solid waste cooperative modifier prepared in Example 1 of the present application;

[0029] Figure 2 The shear strength result diagram of Examples 1-3 and Comparative Examples 1-5 of the present application;

[0030] Figure 3 The void ratio result diagram of Examples 1-3 and Comparative Examples 1-5 of the present application;

[0031] Figure 4 The soil dry-wet cycle process diagram of Example 1 of the present application;

[0032] Figure 5 The weight and unconfined compressive strength process diagram after dry-wet cycle of Example 1 of the present application;

[0033] Figure 6The figure recorded after the modified solidified soil of the cement, the commercial solidifying agent and the solid waste synergistic modifier of the present application was immersed in water for 5 hours;

[0034] Figure 7 The figure of the residual mass change of the solid waste synergistic modifier of the present application and the dry-wet cycle of the comparative examples 2-3. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme of the embodiments of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application. Unless otherwise defined, the professional terms used below are consistent with the meanings understood by those skilled in the art.

[0036] In the following examples, the test materials and reagents used, unless otherwise specified, can be obtained commercially or prepared by known methods.

[0037] Unless otherwise specified, the specific techniques or conditions in the examples can be carried out according to the techniques or conditions described in the literature in the art or according to the product instructions. Unless otherwise specified, the quantitative tests in the following examples are set up with more than three repeated experiments, and the results are averaged.

[0038] Example 1

[0039] A solid waste synergistic modifier, consisting of 4 parts of coal gangue aggregate, 8 parts of steel slag micro-powder, 1.5 parts of desulfurization gypsum, 0.2 parts of polymer reinforcing fiber and 2 parts of Portland cement by mass fraction, which are mixed uniformly.

[0040] The preparation method of the above-mentioned solid waste synergistic modifier comprises the following steps: weighing the raw materials in the above-mentioned mass fraction and mixing uniformly to obtain the solid waste synergistic modifier.

[0041] The specific application of the above-mentioned solid waste synergistic modifier is as follows:

[0042] The silt with a water content of 35% is added at a mixing amount of 15% of the total mass, and rotary tillage is mixed for 5-7 times, and is layered and rolled, with a compaction degree not less than 0.96, to obtain the solidified soil.

[0043] Example 2

[0044] The solid waste synergic modifier is composed of coal gangue aggregate 5 parts, steel slag powder 12 parts, desulfurization gypsum 2 parts, polymer reinforcing fiber 0.4 parts, and silicate cement 4 parts by mass fraction.

[0045] The preparation method of the solid waste synergic modifier comprises the following steps: weighing the raw materials in the above mass fraction, and mixing uniformly to obtain the solid waste synergic modifier.

[0046] The specific application of the solid waste synergic modifier is as follows:

[0047] The solidified soil is obtained by adding 18% of the total mass of the solid waste synergic modifier to the soil with a water content of 30%, and then rotating, mixing, and rolling for 5-7 times.

[0048] Example 3:

[0049] The solid waste synergic modifier is composed of coal gangue aggregate 5 parts, steel slag powder 12 parts, desulfurization gypsum 2 parts, polymer reinforcing fiber 0.4 parts, and silicate cement 4 parts by mass fraction.

[0050] The preparation method of the solid waste synergic modifier comprises the following steps: weighing the raw materials in the above mass fraction, and mixing uniformly to obtain the solid waste synergic modifier.

[0051] The specific application of the solid waste synergic modifier is as follows: adding 20% of the total mass of the solid waste synergic modifier to the soil with a water content of 40%, and then rotating, mixing, and rolling for 5-7 times.

[0052] Comparative Example 1:

[0053] The difference between the comparative example and Example 1 is that the mixing amount of the solid waste synergic modifier is 6% of the total mass of the soil.

[0054] Comparative Example 2:

[0055] The difference between the comparative example and Example 1 is that the mixing amount of the solid waste synergic modifier is 8% of the total mass of the soil.

[0056] Comparative Example 3:

[0057] The difference between the comparative example and Example 1 is that the mixing amount of the solid waste synergic modifier is 12% of the total mass of the soil.

[0058] Comparative Example 4:

[0059] The difference between this comparative example and Example 1 is that the curing agent used is a cement curing agent, and the mixing amount of the cement curing agent is 6%, 8%, 12%, 15%, and 20% of the total mass of the silt.

[0060] Comparative Example 5:

[0061] The difference between this comparative example and the examples is that the curing agent used is a certain commercially available curing agent, and the mixing amount of the curing agent is 6%, 8%, 12%, 15%, and 20% of the total mass of the waste soil or silt.

[0062] Unconfined compressive strength and void ratio test:

[0063] The size of the test block used for the unconfined compressive strength test of the sample is a cylindrical test block with a diameter of 50 mm and a height of 50 mm. The testing equipment is a Shanghai Hengyi HY-10080 electronic universal material testing machine, and the loading rate is 1 mm / min. The test results are the average of three parallel samples. Figure 1 The unconfined compressive strength test process is as follows, and other specific test steps are described in GB / T50123-2019, Figure 2 The shear strength results of Examples 1-3 and Comparative Examples 1-5 are as follows, Figure 3 The influence of Examples 1-3 and Comparative Examples 1-5 on the void ratio of silt curing soil with 95% compaction degree is as follows.

[0064] As shown in Figure 2 , when the mixing amount of the curing agent is 15-20%, the unconfined compressive strength is best. When the mixing amount of the solid waste synergistic modifier is 20%, the unconfined compressive strength reaches 4.77 MPa. When the mixing amount of cement is 20%, the unconfined compressive strength is 3.56 MPa. When the mixing amount of the commercially available curing agent is 20%, the unconfined compressive strength is 3.88 MPa. Therefore, among the three curing agents, the solid waste synergistic modifier has the most significant effect on improving the strength performance of silt soil, followed by the commercially available curing agent, and the least is the cement curing agent.

[0065] As shown in Figure 3 , with the increase of the mixing amount of the curing agent and the quality of the curing agent, the void ratio of the silt curing soil gradually decreases, which has a strengthening effect on the strength of the curing soil.

[0066] Dry-wet cycle test

[0067] Since there is no relevant specification for the dry-wet cycle of curing soil in the domestic related industry, the dry-wet cycle test was carried out according to the American Society for Testing and Materials specification "Standard Test Methods for Wetting and Drying Compacted Soil-Cement Mixtures" (ASTM D559-03). The specific process is shown in Figures 4-5 .

[0068] 1) At the end of the storage in a humid room, the samples are immersed in drinking water at room temperature for 5 hours, then removed. The mass of the test piece and the measured value are determined and recorded.

[0069] 2) Two test pieces are placed in an oven at 70°C for 42 hours, then removed. The mass of the test piece and the measured value are determined and recorded.

[0070] 3) The procedures described in 1 and 2 constitute a wetting and drying cycle (48 hours). The samples are again immersed in water and the procedure is continued for 12 cycles.

[0071] 4) After 12 test cycles, the test pieces are dried at 110°C to constant mass and the mass of the test piece is determined and recorded.

[0072] 5) After 6 cycles and 12 cycles, respectively, the test pieces are dried at 110°C to constant mass and the compressive strength of the test pieces is measured and recorded.

[0073] The wetting and drying cycle test simulates the change of water environment according to the above steps, and cement, a commercially available solidifying agent and the solid waste synergistic modifier of the present application are selected as solidifying materials to compare the mass loss ratio and strength loss of the modified silt soil samples, and the results are shown in Figure 6 Before the experiment, a water immersion test was first carried out, in which the cement content was 6% and 12%, and the solidified soil appeared to be disintegrated, and at a high cement content, the disintegration phenomenon was more severe. When the content of the commercially available solidifying agent was 8% and 15%, the solidified soil also appeared to be disintegrated, and at a higher content of the solidifying agent, the disintegration phenomenon was more obvious. When the content of the solid waste synergistic modifier was 8%, the solidified soil appeared to be slightly disintegrated at the corners of the test piece, and the overall structure was not damaged; when the content was 15%, the solidified agent did not appear to be significantly disintegrated, the surface was smooth and the structure was complete, which proves that the ability of the solidified soil to resist wetting and drying cycles is solid waste synergistic modifier > commercially available solidifying agent > cement.

[0074] In view of the fact that the solid waste synergistic modifier did not dissolve in the water immersion test, subsequent wetting and drying cycle tests were carried out, and the dry weight of the solidified soil was recorded after each wetting and drying cycle, and the change in residual mass is shown in Figure 7The solidified soil with 8% of the solid waste synergistic modifier has partial disintegration at the corners and the overall structure is perfect; the solidified soil with 12% and 15% of the solid waste synergistic modifier does not have obvious disintegration and the overall structure is perfect. When the cycle is carried out for 12 times, the solidified soil with 8% and 12% of the solid waste synergistic modifier has partial disintegration at the corners and the overall structure is perfect; the solidified soil with 15% of the solid waste synergistic modifier does not have obvious disintegration and the overall structure is perfect. In order to explore the structure attenuation after the dry-wet cycle, the unconfined compressive strength is measured and recorded before the cycle, the 6th cycle and the 12th cycle. Table 1 below records the strength changes before the dry-wet cycle, after the dry-wet cycle for 6 times and 12 times.

[0075] Table 1 Dry-wet cycle record

[0076]

[0077] The above phenomenon is due to the fact that cement and silt are combined with water to produce hydration reaction, but cement and silt do not react, the hydration product generated by the reaction of cement and water accounts for a small proportion of the entire silt solidified body, and the part of the silt solidified body not wrapped by the hydration product is decomposed in water after the silt solidified body is soaked in water, resulting in disintegration of the silt solidified body. In addition, the commercially available solidifying agent mainly plays a role in filling the pores of the solidified soil, although it can significantly improve the strength of the solidified soil, but it does not effectively improve the water erosion resistance of the solidified soil, and its mechanism is similar to that of cement. The components of the solid waste synergistic modifier have certain differences in the modification effect of silt, on the one hand, they can play a role in densifying the structure of the solidified soil, and on the other hand, they can play a role in stimulating the depolymerization of clay substances. The components of the solid waste synergistic modifier directly react with silt, the layered clay mineral is depolymerized into a more active sheet structure, so that the solid waste synergistic modifier and the clay form a more compact cementation contact. With the increase of the content of the solid waste synergistic modifier, the cementation structure formed is more compact, the water erosion resistance is enhanced, and the surface of the solidified soil is smoother, so the erosion resistance is stronger.

[0078] The above examples are only used to illustrate the technical solutions of the present application, but not limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A solid waste synergistic modifier characterized in that, The raw materials include, in terms of mass fraction, 4-5 parts of coal gangue aggregate, 8-12 parts of steel slag powder, 1.5-2 parts of desulfurization gypsum, 0.2-0.4 parts of polymer reinforcing fiber and 2-4 parts of Portland cement.

2. The solid waste synergistic modifier of claim 1, wherein, Preferably, the raw materials include 4.3-4.8 parts of coal gangue aggregate, 10-11 parts of steel slag powder, 1.8-2 parts of desulfurization gypsum, 0.3-0.4 parts of polymer reinforcing fiber and 2.5-3.5 parts of Portland cement.

3. The solid waste co-modifier of claim 1, wherein, The coal gangue aggregate is angular particle with a particle size of 0.5-2 mm.

4. The solid waste co-modifier of claim 1, wherein, The polymer reinforcing fiber is polypropylene fiber with a length of 10-15 mm.

5. The method of making a solid waste synergistic modifier of any one of claims 1-4, characterized in that, The method includes the following steps: weighing the raw materials in terms of mass fraction and mixing them uniformly.

6. Use of the solid waste synergistic modifier according to any one of claims 1-4 for solidifying waste soil or sludge, characterized in that, The method includes the following steps: mixing the solid waste synergistic modifier with waste soil or silt, stirring, compacting and obtaining solidified soil.

7. Use according to claim 6, characterized in that, The mixing amount of the solid waste synergistic modifier is 15%-20% of the total mass of the waste soil or silt.

8. Use according to claim 6, characterized in that, The water content of the waste soil or silt is 30%-40%.

9. Use according to claim 6, characterized in that, The stirring is rotary tillage mixing for 5-7 times.

10. Use according to claim 6, characterized in that, The compacting method is layering and rolling, and the compactness is not less than 0.96.

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