Fluidized solidified soil based on high-water-content sludge and preparation method thereof

Abstract

The invention provides flow-state solidified soil based on high-water-content sludge and a preparation method of the flow-state solidified soil, and belongs to the technical field of civil engineering. The flow-state solidified soil comprises high-water-content sludge and further comprises the following raw material components in percentage by mass: ardealite accounting for 10-20% of the absolute dry mass of the high-water-content sludge; the fly ash accounts for 24-40% of the absolutely dry mass of the high-water-content sludge; the polyacrylate emulsion accounts for 2-4% of the absolutely dry mass of the high-water-content sludge; the alkali activator accounts for 6-8% of the absolute dry mass of the high-water-content sludge; the mass of the added water is calculated according to the water-solid ratio. According to the invention, the resource reutilization of the high-water-content sludge can be realized, the cement consumption can be reduced, and the production cost of the solidified soil can be reduced.

Description

Technical Field

[0001] The invention relates to the technical field of civil engineering, and in particular to a fluidized solidified soil based on high-water content sludge and a preparation method thereof. Background Art

[0002] With the rapid development of urbanization, a large amount of high-moisture silt with a moisture content of more than 60% is brought about during river dredging and subway construction. Due to its high moisture content, high-moisture silt is physically unstable and in a fluid or plastic state, making it difficult to fix and shape. This characteristic makes it unable to provide sufficient strength and stability when used as a building material, which is not conducive to direct engineering application. Dehydration is required for reuse, and traditional physical dehydration methods are mainly natural drying and mechanical dehydration, which have problems such as large footprint, high time cost, limited dehydration efficiency, and inability to completely remove moisture. In addition, the treated silt still needs to be further processed to meet application requirements. The overall process is complicated and costly.

[0003] The mainstream method of resource treatment of existing high-water content sludge is to solidify it by adding a solidifying agent (such as cement) to convert it into geotechnical engineering materials, thereby utilizing it as a resource and turning waste into treasure. For high-water content sludge with an initial water content greater than 60%, the traditional treatment method is generally to increase the cement content to meet the solidification requirements, but the cost of cement is relatively high. Increasing the content will significantly increase its production cost, which is not conducive to application and promotion. Fluidized solidified soil is a new type of building material with self-weight fluidity or low plasticity, which can harden within a certain period of time and obtain a certain strength. It is usually mixed with fine-grained soil, cement, water and additives (such as fly ash, slag powder, etc.). The characteristic of fluidized solidified soil is that it can flow into the space that needs to be filled without vibration, and then solidify within a set time, thereby reducing the impact on surrounding structures.

[0004] If high-water-content silt is used to replace cement to prepare fluidized solidified soil, it can not only realize the resource recycling of high-water-content silt, but also save the production cost of fluidized solidified soil. Summary of the invention

[0005] To achieve the above object, the present invention provides a fluidized solidified soil based on high-water content sludge and a preparation method thereof.

[0006] The technical solution adopted by the present invention is:

[0007] A fluidized solidified soil based on high-water content silt, comprising high-water content silt and the following raw material components in percentage by weight:

[0008] Phosphogypsum, which is 10-20% of the absolute dry mass of the high-water content sludge;

[0009] Fly ash, which is 24-40% of the absolute dry mass of the high-water content sludge;

[0010] Polyacrylate emulsion, which is 2-4% of the absolute dry mass of the high-water content sludge;

[0011] Alkali activator, which is 6-8% of the absolute dry mass of the high-water content sludge;

[0012] The mass of added water is calculated according to the following formula:

[0013] m 添 =xm 总 -m 淤泥 w;

[0014] In the formula, m 添 is the mass of added water, x is the water-to-solid ratio, x = 0.56 ~ 0.62, m 总 is the sum of the mass of phosphogypsum, fly ash and high-water content sludge, m 淤泥 is the mass of high-water content sludge, w is the initial water content of high-water content sludge. The water content of high-water content sludge is the ratio of the water mass contained in the high-water content sludge to the absolute dry mass of the sludge.

[0015] Furthermore, the fluidity value of the fluidized solidified soil is 160-220 m, and the 28-day unconfined compressive strength is ≥560 kPa. The cost is more economical.

[0016] Furthermore, the high-water content sludge is dredged sludge, and its initial water content is 60-80%, which is beneficial to improving the strength of the solidified soil and saving costs.

[0017] Furthermore, the alkaline activator is an aqueous solution of solid potassium hydroxide, and its molar concentration is 12-16 mol / L.

[0018] Using potassium hydroxide solution as an alkali activator can further promote the release of aluminosilicate in fly ash and participate in the reaction, forming a high-strength gel network and improving the strength of solidified soil. Solid potassium hydroxide is easy to transport and store. Using solid potassium hydroxide to prepare alkali activators can reduce the production cost of solidified soil.

[0019] Furthermore, the CaSO4·2H2O content of the phosphogypsum is greater than 75%, which is beneficial to further improve the strength of the solidified soil.

[0020] Furthermore, the fly ash is Class F secondary fly ash, and the total content of SiO2 and Al2O3 thereof is greater than 80%, thereby further improving the strength of the solidified soil.

[0021] Any one of the above methods for preparing fluidized solidified soil based on high-water content sludge comprises the following steps:

[0022] Step 1: using solid potassium hydroxide to prepare a potassium hydroxide solution to obtain an alkaline activator;

[0023] Step 2: measuring the water content of the prepared high-water content sludge, and then mixing the high-water content sludge with fly ash and phosphogypsum in a stirring pot;

[0024] Step 3: Mix the alkaline activator prepared in step 1 with water and stir evenly, then add it to the mixture prepared in step 2, and continue stirring for a period of time;

[0025] Step 4: Add polyacrylate emulsion to the mixture prepared in step 3, and continue stirring for a period of time to obtain fluidized solidified soil based on high-water content sludge.

[0026] Furthermore, in step 1, the potassium hydroxide solution is prepared under the conditions of: preparing at 25°C±2°C 24 hours in advance, thereby reducing the influence of reaction heat during the preparation process and ensuring production safety.

[0027] Furthermore, the stirring speed of step 2 is 200-250 r / min, and the stirring time is 3-5 min. The stirring speed of step 3 is 450-600 r / min, and the stirring time is 15-20 min. The stirring speed of step 4 is 400-450 r / min, and the stirring time is 3-5 min.

[0028] By controlling the stirring speed and stirring time in the above steps, the activation effect of the alkali activator can be further promoted, thereby improving the reaction effect of phosphogypsum and fly ash with water.

[0029] The beneficial effects of the present invention are:

[0030] 1. Under the action of alkaline activators, active components such as SiO2, Al2O3 and CaO in phosphogypsum and fly ash are activated to generate honeycomb network gels (such as CSH and NASH gels) and needle-rod-shaped calcium sulfonate crystals with cementitious properties. The three-dimensional network gels are linked and aggregated to form a large number of flocculent gel aggregates under the action of cementation, and adhere to the surface of the soil particles of the silt to form particle aggregates of different sizes, while the tiny needle-shaped calcium sulfonate crystals also fill the gaps between the aggregates, thus constructing a dense skeleton space structure and enhancing the strength and stability of the soil; in addition, the slight volume expansion of phosphogypsum when it meets water can further fill the pores between soil particles and improve the early strength of the solidified soil, while the calcium sulfonate generated by its hydration can play the role of "micro-reinforcement", bridging soil particles, hydrated gel aggregates and unhydrated solidified particles, and enhancing the integrity of the solidified soil system. The synergistic effect of the gelling system formed by the polyacrylate emulsion and the alkali-induced reaction further enhances the strength of the solidified soil. The flow value of the prepared fluidized solidified soil reaches 160mm to 220mm, and the 28d unconfined compressive strength is ≥560kPa.

[0031] 2. The present invention can realize the resource recycling of high-water content sludge. By using alkali-activated phosphogypsum, fly ash and polyacrylate emulsion polymer materials as cementitious materials to replace cement to prepare fluidized solidified soil, the amount of cement used can be reduced and the production cost can be reduced.

[0032] 3. The preparation method of the present invention is simple, and the fluidized solidified soil obtained is widely used. It can be used for backfilling and pouring of various foundation pits and mine pits, and can also be widely used in reinforcement fields such as roadbeds and building foundations. DETAILED DESCRIPTION

[0033] The technical solution of the present invention is further described below in conjunction with embodiments.

[0034] The high-water content sludge used in the following examples is dredged sludge produced by the Shandong Tai'an River dredging project, and its initial water content is 60-80%.

[0035] The polyacrylate emulsion used was produced by Zibo Junwu Chemical Co., Ltd.

[0036] Example 1

[0037] A fluidized solidified soil based on high-water content silt, the raw materials of which are:

[0038] 1422.1 kg of high-water content sludge, with an initial water content of 62.3%;

[0039] 213.3kg fly ash, with a total content of SiO2 and Al2O3 of 170.6kg;

[0040] 113.8 kg of phosphogypsum, with a CaSO4·2H2O content of 85.4 kg;

[0041] Polyacrylate emulsion 17.5kg;

[0042] 52.6 kg of potassium hydroxide solution, with a molar concentration of 14 mol / L;

[0043] Water 128.6kg.

[0044] The preparation method of the above-mentioned fluidized solidified soil is as follows:

[0045] Step 1: Prepare potassium hydroxide solution 24 hours in advance as an alkaline activator;

[0046] Step 2: Determine the moisture content of the prepared high-moisture sludge, and then mix the high-moisture sludge with fly ash and phosphogypsum in a stirring pot for 4 minutes at a stirring speed of 220 r / min;

[0047] Step 3: Mix the alkaline activator solution prepared in step 1 with water and stir evenly, then add it to the mixture prepared in step 2, and stir at a stirring speed of 460 r / min for 18 minutes;

[0048] Step 4: Add polyacrylate emulsion to the mixture prepared in step 3, stir for 4 minutes at a stirring speed of 430 r / min, and obtain fluidized solidified soil based on high-water content sludge.

[0049] Example 2

[0050] A fluidized solidified soil based on high-water content silt, the raw materials of which are:

[0051] 1361.24kg of high-water content sludge, with an initial water content of 68%;

[0052] 245.0kg fly ash, total content of SiO2 and Al2O3 is 196kg;

[0053] 136.1 kg of phosphogypsum, with a CaSO4·2H2O content of 102.1 kg;

[0054] Polyacrylate emulsion 24.3kg;

[0055] 57.2 kg of potassium hydroxide solution, with a molar concentration of 14 mol / L.

[0056] Water 154.6kg.

[0057] The preparation method of the above-mentioned fluidized solidified soil is basically the same as that of Example 1, except that the stirring speed of step 2 is 250 r / min, and the stirring time is 3 min; the stirring speed of step 3 is 600 r / min, and the stirring time is 15 min; and the stirring speed of step 4 is 450 r / min, and the stirring time is 3 min.

[0058] Example 3

[0059] 1478.37kg of high-water content sludge, with an initial water content of 71.2%;

[0060] Fly ash 295.67kg, total content of SiO2 and Al2O3 236.5kg;

[0061] 147.8kg of phosphogypsum, with a CaSO4·2H2O content of 110.8kg;

[0062] Polyacrylate emulsion 21.6kg;

[0063] 66.5 kg of potassium hydroxide solution, with a molar concentration of 16 mol / L.

[0064] Water 177.4kg.

[0065] The preparation method of the above-mentioned fluidized solidified soil is basically the same as that of Example 1, except that the stirring speed of step 2 is 200 r / min, and the stirring time is 5 min; the stirring speed of step 3 is 450 r / min, and the stirring time is 20 min; and the stirring speed of step 4 is 400 r / min, and the stirring time is 5 min.

[0066] The fluidity and unconfined compressive strength of the fluidized solidified soil prepared in Examples 1 to 3 were tested by the following method. The results are shown in Table 1.

[0067] 1) Liquidity test

[0068] The fluidity test device consists of a plexiglass plate and a plexiglass double-opening cylinder with a height of 80mm and an inner diameter of 80mm. During the test, first use a rag to wet the inner wall of the cylinder and the surface of the glass plate, and place the cylinder in the middle of the horizontal glass plate; then load the newly mixed fluid soil sample into the cylinder, and continuously vibrate during the loading process to expel bubbles to ensure that the sample is dense, and use a scraper to flatten the surface after filling; after the loading is completed, gently lift the plexiglass cylinder vertically upwards, and after 30 seconds or when the soil sample no longer spreads, use a steel ruler to measure the maximum diameter and minimum diameter of the mixture after spreading, and take the average of the two as the flow value. In order to ensure the reliability of the test, each group of samples needs to be tested 2 to 3 times in parallel, and the average value is taken as the final flow value;

[0069] 2) Unconfined compressive strength test

[0070] The unconfined compressive strength test is carried out in accordance with the "Standard for Geotechnical Test Methods" (GB / T50123~2019).

[0071] Table 1

[0072]

[0073] It can be seen from Table 1 that the fluidized solidified soil prepared by the present invention has a flow value of 160 mm to 220 mm, a 3-day unconfined compressive strength of >200 kPa, a 7-day unconfined compressive strength of >300 kPa, and a 28-day unconfined compressive strength of >750 kPa, which meets the requirements for engineering use.

[0074] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. A fluidized solidified soil based on high-water content sludge, comprising high-water content sludge, characterized in that: It also includes the following raw material components in percentage by weight: Phosphogypsum, which is 10-20% of the absolute dry mass of the high-water content sludge; Fly ash, which is 24-40% of the absolute dry mass of the high-water content sludge; Polyacrylate emulsion, which is 2-4% of the absolute dry mass of the high-water content sludge; Alkali activator, which is 6-8% of the absolute dry mass of the high-water content sludge; The mass of added water is calculated according to the following formula: m 添 =xm 总 -m 淤泥 w; In the formula, m 添 is the mass of added water, x is the water-to-solid ratio, x = 0.56 ~ 0.62, m 总 is the sum of the mass of phosphogypsum, fly ash and high-water content sludge, m 淤泥 is the mass of high-water content sludge, and w is the initial water content of high-water content sludge.

2. The fluidized solidified soil based on high-water content silt according to claim 1, characterized in that: The fluidity value of the fluidized solidified soil is 160-220 m, and the 28-day unconfined compressive strength is ≥560 kPa.

3. The fluidized solidified soil based on high-water content sludge according to claim 1, characterized in that: The high-water content sludge is dredged sludge, and its initial water content is 60-80%.

4. The fluidized solidified soil based on high-water content sludge according to claim 1, characterized in that: The alkaline activator is an aqueous solution of solid potassium hydroxide, and the molar concentration thereof is 12-16 mol / L.

5. The fluidized solidified soil based on high-water content sludge according to claim 1, characterized in that: The CaSO4·2H2O content of the phosphogypsum is greater than 75%.

6. The fluidized solidified soil based on high-water content sludge according to claim 1, characterized in that: The fly ash is Class F secondary fly ash, and the total content of SiO2 and Al2O3 thereof is greater than 80%.

7. A method for preparing fluidized solidified soil based on high-water content sludge according to any one of claims 1 to 6, characterized in that: The following steps are involved: Step 1: using solid potassium hydroxide to prepare a potassium hydroxide solution to obtain an alkaline activator; Step 2: measuring the water content of the prepared high-water content sludge, and then mixing the high-water content sludge with fly ash and phosphogypsum in a stirring pot; Step 3: Mix the alkaline activator prepared in step 1 with water and stir evenly, then add it to the mixture prepared in step 2, and continue stirring for a period of time; Step 4: Add polyacrylate emulsion to the mixture prepared in step 3, and continue stirring for a period of time to obtain fluidized solidified soil based on high-water content sludge.

8. The preparation method according to claim 7, characterized in that: In step 1, the preparation condition of the potassium hydroxide solution is: prepared at 25°C ± 2°C 24 hours in advance.

9. The preparation method according to claim 7, characterized in that: The stirring speed of step 2 is 200-250 r / min, and the stirring time is 3-5 min. The stirring speed of step 3 is 450-600 r / min, and the stirring time is 15-20 min. The stirring speed of step 4 is 400-450 r / min, and the stirring time is 3-5 min.

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