A method for resource utilization of highly water-containing silty engineering muck

Abstract

The present invention provides a method for resource utilization of highly water-containing silt engineering muck, comprising the following steps: S1. Adding a curing agent to the highly water-containing silt engineering muck for mixing, then performing dehydration treatment, and then performing crushing and screening to obtain semi-finished muck; S2. Placing the semi-finished muck into a carbonization chamber for carbonization curing to obtain a carbonized soil mixture; S3. Mixing the carbonized soil with cement, admixture, aggregate and sodium bicarbonate to obtain a carbonized and cured soil mixture; S4. Performing crushing and screening on the carbonized and cured soil mixture, spreading and rolling to obtain a base material. The high-performance road-use material obtained by the method of the present invention has high strength, high water stability coefficient and good frost resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of the reuse of highly water-containing silt-like engineering muck, and particularly relates to a method for the resource utilization of highly water-containing silt-like engineering muck. Background Art

[0002] The main characteristics of highly water-containing silt-like engineering muck are as follows: high water content, extremely fine particles, good water adsorption property, poor water permeability and air permeability, weak bearing capacity, high clay particle content and very high viscosity. Its property is like plasticine, with extremely strong viscosity and no fluidity. Some muck also wraps and adheres to a certain amount of impurities such as large stones and construction waste (especially excavation muck, with more impurities). The resource utilization is extremely difficult. To ultimately achieve the large-scale resource utilization of this kind of muck, whether it is the utilization of soil materials or building materials, it needs to be dehydrated and dried and then subjected to secondary deep processing to achieve.

[0003] Currently, in the research on the resource utilization of most highly water-containing silt-like engineering muck as roadbed materials, there are problems such as complex processes, high costs, low treatment efficiency, and unstable product performance. The main processes are as follows: 1. The muck is diluted with water into slurry, then dewatered by plate and frame pressure filtration, and then a curing agent is added to the pressure-filtered mud cake for uniform mixing to form roadbed materials. This process has problems such as low treatment efficiency, high cost, and unqualified product performance; 2. Natural drying is adopted, combined with mechanical turning and throwing for dehydration, and then a curing agent is added to the dehydrated muck to produce roadbed materials. This method has problems such as low production capacity and being easily affected by weather; 3. The mechanical thermal dehydration method also has problems such as high production cost, insufficient treatment capacity, and being not energy-saving and environmentally friendly; 4. Currently, the curing agents used for preparing roadbed materials are mainly inorganic curing agents and organic curing agents. Since the roadbed materials themselves have requirements for mechanical properties, the use of two curing agents in combination is required to meet the requirements. The use of organic curing agents will have problems such as uneven mixing and environmental pollution. Therefore, for the resource utilization of highly water-containing silt-like engineering muck as base course materials, there is no method with simple process, stable product performance, low cost, environmental protection and no pollution, and capable of continuous large-scale treatment. Summary of the Invention

[0004] The purpose of the invention is to provide a method for the resource utilization of highly water-containing silt-like engineering muck, aiming at the deficiencies of the existing technology for the resource utilization of muck as base course materials, and solving the problems such as complex resource utilization process of silt-like engineering muck, unstable product performance, and high cost, so as to achieve the purpose of continuous, large-scale and efficient resource utilization of this kind of muck.

[0005] Based on the above purpose, the invention provides a method for the resource utilization of highly water-containing silt-like engineering muck, which comprises the following steps:

[0006] S1. Add the highly water - containing silt - like engineering muck to a curing agent for mixed dehydration treatment, then perform crushing, impurity removal, and screening to obtain semi - finished muck.

[0007] S2. Place the semi - finished muck into a carbonization chamber for carbonization curing to obtain a carbonized soil mixture.

[0008] S3. Mix the carbonized soil with cement, admixture, aggregate, and sodium bicarbonate, and supplement water as needed to the optimal moisture content to obtain a carbonized and solidified soil mixture.

[0009] S4. Crush and screen the carbonized and solidified soil mixture, and then perform paving and rolling to obtain base course materials.

[0010] Furthermore, the highly water - containing silt - like engineering muck is in a plastic state, with a moisture content of 50% - 60%, an organic matter content of 5% - 10%, and more than 10% of particles with a particle size greater than 50mm.

[0011] Furthermore, S1 specifically includes the following steps: a. Dehydration treatment: Stir the highly water - containing silt - like engineering muck and the curing agent evenly through a powerful stirring head device, and turn it over with an excavator for natural curing until the moisture content of the muck drops below 20%; b. Crushing and impurity removal treatment: Crush and screen the dehydrated muck through a screening bucket, take particles with a particle size below 50mm, and remove the part with a particle size above 50mm as impurities; c. Screening treatment: Crush and screen the muck after impurity removal again through a crushing and screening bucket device to obtain semi - finished muck with a particle size below 15mm.

[0012] Furthermore, according to the method described in claim 1, the curing agent in step S1 includes steel slag powder, quicklime, reactive magnesium oxide, and cement clinker, and their dosages are 1 - 10%, 1 - 6%, 0.5 - 1%, and 1 - 10% of the mass of the highly water - containing silt - like engineering muck respectively.

[0013] Furthermore, the curing agent in step S1 also includes power plant desulfurization ash or high - calcium fly ash, where the dosage of power plant desulfurization ash is 1 - 3% of the mass of the highly water - containing silt - like engineering muck, and the dosage of high - calcium fly ash is 1 - 7% of the mass of the highly water - containing silt - like engineering muck.

[0014] Furthermore, during the carbonization curing in step S2, the curing humidity is 60 - 70%, the carbon dioxide pressure is 100 - 300Kpa, the carbon dioxide volume concentration is 80 - 90%, and the carbonization time is 3 - 6h.

[0015] Furthermore, the mass ratio of the carbonized soil to cement, admixture, aggregate, and sodium bicarbonate in S3 is 100:1 - 3:0.5 - 2:1 - 5:0.1 - 0.8.

[0016] Furthermore, the aggregate is construction waste with a particle size less than 15 mm, and the content of particles less than 10 mm is ≥ 75%.

[0017] Furthermore, after screening by the crushing and screening bucket in S4, the particle size of the mixed material is ≤ 15 mm.

[0018] The present invention also relates to a road material prepared by the above method.

[0019] The present invention has the following beneficial effects:

[0020] In the present invention, the pretreatment process first mixes steel slag powder, quicklime, reactive magnesium oxide and cement clinker with silt engineering soil, and power plant desulfurized ash and / or high-calcium fly ash can also be added. Through physical and chemical actions, its moisture content is reduced, and combined with carbonation curing, the second reduction of its moisture content is achieved. Finally, the moisture content of the silt engineering soil can be reduced to about the optimal moisture content.

[0021] Among them, on the one hand, quicklime has water absorption and can reduce the moisture content of silt soil. On the other hand, it can react with water in the silt soil to generate Ca(OH) 2 , providing an alkaline environment for the hydration reactions of cement clinker, fly ash, steel slag powder, etc. The generated Ca(OH) 2 can also participate in the carbonation reaction to generate crystalline CaCO 3 , further reducing the moisture content of silt. Adding reactive magnesium oxide can react with the water in the silt engineering soil to generate crystalline Mg(OH) 2 , which can enhance the strength of the soil, and can subsequently react with CO 2 to generate prismatic MgCO 3 ·3H 2 O and 4MgCO 3 ·Mg(OH) 2 ·4H 2 O and other crystalline carbonation products, which can reduce the moisture content of the silt engineering soil and improve its mechanical properties; steel slag powder has a skeleton effect, opening the water permeation channels of the silt engineering soil and increasing the void spacing between soil particles, accelerating the dehydration rate, and being beneficial to subsequent CO 2Full carbonization reaction occurs in the muck, reducing the water content of the muck and improving its mechanical properties. There are active components in the steel slag powder that undergo hydration reaction in an alkaline environment to generate hydration products, reducing the water content of the muck and improving its mechanical properties. Moreover, there is free calcium oxide in the steel slag powder itself, which can participate in both hydration reaction and carbonization reaction. The desulfurized ash from power plants, high-calcium fly ash, and cement clinker can undergo hydration reaction, pozzolanic reaction, and carbonization reaction with the mucky muck, and finally form hydration products such as calcium silicate hydrate C-S-H, calcium aluminate hydrate C-A-H, ettringite, and carbonization products, reducing the water content of the muck and improving its mechanical properties.

[0022] The carbonized material of the present invention can react with water in the mucky muck after adding cement to generate hydration products and Ca(OH) 2 , and the silicon-aluminum active components in the ultrafine powder admixture react to generate calcium silicate hydrate C-S-H, calcium aluminate hydrate C-A-H, and ettringite under the action of Ca(OH) 2 , improving the mechanical properties, stability, and durability of the base material. The sodium bicarbonate particles can decompose to generate sodium carbonate and carbon dioxide. Among them, sodium carbonate has a promoting effect on the cement hydration reaction, improving the stone formation rate, and carbon dioxide can be used as a carbon source for the carbonization reaction to further react with the excessive Ca(OH) 2 , magnesium oxide, calcium silicate hydrate C-S-H, and calcium aluminate hydrate C-A-H in the system to generate carbonization products. The construction waste aggregate mainly plays a role as a skeleton, improving the mechanical properties of the subgrade material. Under the synergistic action of the above several materials, the generated hydration products and crystalline carbonization products fill the pores of the mucky engineering muck, making it overall dense and improving the working performance of the road-use material prepared therefrom, realizing the transformation of high-water-content mucky engineering muck into high-performance highway base materials.

[0023] The high-performance base material obtained by using the method provided by the present invention has an organic matter content of ≤5%, and after paving and compaction, it is used as a road-use material with a compaction degree of ≥96%, a 7-day unconfined compressive strength of ≥4.5 Mpa, a water stability coefficient of ≥85%, and a 28-day frost resistance index of ≥80%.

[0024] The beneficial effects of the present invention:

[0025] (1) The present invention not only reasonably and effectively solves the problems of environmental pollution such as random stacking, filling, and throwing of high-water-content mucky engineering muck, but also uses the treated muck as a base material, greatly reducing the consumption of traditional soil materials, avoiding the environmental and energy problems caused during the production of traditional crushed stone, pond slag, and water-stabilized materials, reducing the damage to mountain resources, and achieving the purpose of harmless and resourceful treatment of engineering muck.

[0026] (2) The present invention can efficiently, low-cost, continuously and on a large scale treat high-water-content silty slag with a simple process. The road base or subbase of urban expressways and trunk roads prepared by the present invention has excellent mechanical properties, high stability, good water resistance, low carbon and environmental protection, and high added value. It can completely or partially replace traditional slag, pond residue and water-stabilized material, and has a good market prospect.

[0027] (3) The pretreatment dehydration process of the present invention is simple. The pretreatment equipment only needs a powerful stirring head and a screening bucket to solve the problems of dehydration, impurity removal and screening. The raw materials of the curing agent used are basically solid waste, which is cheap and easy to obtain. Compared with the current disposal process, the disposal cost is reduced and has broad engineering application prospects.

[0028] (4) Compared with the current mainstream treatment process, the road material of the present invention does not require long-term maintenance. It only takes three days to reach the optimal moisture content of the road material and related mechanical performance indicators, thereby improving production efficiency.

[0029] (5) During the preparation process of the road material of the present invention, a large amount of industrial waste gas CO is absorbed by carbonization. 2 , which is conducive to reducing the greenhouse effect and is in line with my country's dual carbon policy. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0031] The embodiments of the present invention will be described in detail below with reference to examples, but those skilled in the art will appreciate that the following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention.

[0032] Example 1

[0033] A method for resource utilization of high-water-content silty engineering slag, specifically comprising the following steps:

[0034] (1) The relevant indicators of muddy engineering slag in a coastal area of ​​Zhejiang Province were tested, and the moisture content of the muddy engineering slag was 53.1%, the organic matter content was 6.2%, and the proportion of particles ≥50 mm was about 13%. The high-water-content muddy engineering slag was mixed with a curing agent, dehydrated, crushed, impurity-removed and screened to obtain a semi-finished slag; the curing agent is shown in Table 1.

[0035] Table 1

[0036]

[0037]

[0038] Note: % is mass percentage.

[0039] During specific treatment, after the curing agent and the muck are fully stirred by a powerful stirring head, they are turned over by an excavator and naturally cured for 3 days. After that, the water content of the muck is reduced to less than 20%. Then, it is screened by a screening bucket to remove large particle stones or garbage to ensure uniform particle size of the mixture. Finally, it is crushed and screened by the screening bucket so that the particle size of the material does not exceed 15 mm, and semi-finished muck is obtained.

[0040] (2) Put the semi-finished muck mixture into a carbonization curing device for CO 2 carbonization curing. The carbonization curing conditions are: curing humidity is 65%, carbon dioxide pressure is 280 Kpa, carbon dioxide concentration is 80%, and carbonization time is 4 h, and carbonized soil mixture is obtained.

[0041] (3) Transport the carbonized soil mixture, cement clinker with an admixture of 2%, ultra-fine powder admixture with an admixture of 1%, construction waste aggregate with an admixture of 1.5%, and sodium bicarbonate with an admixture of 0.5% to a homogenizer and stir evenly. After sufficient and uniform stirring, a carbonized and cured mixture can be obtained.

[0042] (4) Crush and screen the carbonized and cured soil mixture through a screening bucket, with the particle size of the material not exceeding 15 mm. Spread it on the cleared site. After spreading and leveling, use a 20t roller to roll it, and qualified road-use materials are obtained. After measurement, the optimum water content, maximum dry density and in-situ compaction degree of the road-use mixture are shown in Table 2 below. Refer to the "Test Regulations for Inorganic Binding Material Stabilized Materials in Highway Engineering" to form the in-situ mixture, and measure the 7-day unconfined compressive strength after curing. The water stability coefficient and frost resistance index are shown in Table 2. This carbonized and cured road-use material can be used for the filling of the base course of the main road.

[0043] Table 2

[0044]

[0045]

[0046] As can be seen from the above table, when the curing agent lacks materials such as steel slag powder, quicklime, and reactive magnesium oxide, the unconfined compressive strength, water stability and frost resistance of the base course material will be affected.

[0047] Example 2

[0048] (1) The muddy engineering slag from a coastal area of ​​Guangdong was tested for relevant indicators, and the moisture content of the muddy engineering slag was 57.8% and the organic matter content was 8.5%. 2% of steel slag powder, 2% of quicklime, 1.5% of dehydrated ash from a power plant, 2% of high-calcium fly ash, 1% of active magnesium oxide, and 2% of cement clinker were added to the slag, and after being fully stirred by a mixing head, the slag was turned over by an excavator. After natural curing, the moisture content of the slag was reduced to less than 20%, and then it was screened by a vibrating screen to remove large particles of stone or garbage to ensure that the particle size of the mixture was uniform. Finally, it was crushed and screened by a screening bucket to make the particle size of the material not higher than 15 mm, and a semi-finished slag was obtained.

[0049] (2) Place the semi-finished slag into the carbonization curing device for CO 2 Carbonization curing: the carbonization curing conditions are as follows: curing humidity is 60%, carbon dioxide pressure is 300Kpa, carbon dioxide concentration is 90%, and carbonization time is 6h to obtain a carbonized soil mixture.

[0050] (3) The carbonized soil mixture is mixed with cement clinker, ultrafine powder admixture, construction waste aggregate and sodium bicarbonate. The specific proportions are shown in Table 3 below. After mixing, it is conveyed to a homogenizer for mixing evenly. The carbonized solidified mixture can be obtained by fully mixing.

[0051] Table 3

[0052]

[0053] (4) The carbonized solidified soil mixture is crushed and screened through a screening bucket. The material particle size is not higher than 15 mm. It is spread on the site after the surface is cleared. After spreading and leveling, it is rolled with a 20t roller to obtain qualified road materials. The optimal moisture content, maximum dry density and on-site compaction degree of the road mixture are measured and shown in Table 4 below. The on-site mixture is molded in accordance with the "Test Procedures for Stabilized Materials of Inorganic Binders for Highway Engineering". After curing, the 7-day unconfined compressive strength, water stability coefficient and antifreeze index are measured and shown in Table 4. The carbonized solidified soil road material can be used for filling the main road base.

[0054] Table 4

[0055]

[0056] It can be seen from the above table that not adding sodium bicarbonate will lead to a significant decrease in the water stability and frost resistance of the base material.

[0057] Example 3

[0058] (1) The muddy engineering slag from a coastal area of ​​Jiangsu Province was tested for relevant indicators, and the moisture content of the muddy engineering slag was 59.2%, and the organic matter content was 5.3%. 2.5% of steel slag powder, 4% of quicklime, 2% of dehydrated ash from power plants, 0.5% of active magnesium oxide, 1% of cement clinker and slag were fully mixed with a powerful mixing head, and then turned over by an excavator. After natural curing, the moisture content of the slag was reduced to below 20%, and then screened with a vibrating screen to remove large particles of stone or garbage to ensure that the particle size of the mixture was uniform. Finally, the material was crushed and screened with a screening bucket to make the particle size of the material no higher than 15 mm, and a semi-finished slag was obtained.

[0059] (2) Place the semi-finished slag into the carbonization curing device for CO 2 Carbonization curing: the carbonization curing conditions are as follows: curing humidity is 60%, carbon dioxide pressure is 100Kpa, carbon dioxide concentration is 80%, and carbonization time is 3h to obtain a carbonized solidified soil mixture.

[0060] (3) The carbonized soil mixture is mixed with 1% cement clinker, 2% ultrafine powder admixture, 1.9% construction waste aggregate, and 0.1% sodium bicarbonate, and transported to a homogenizer for uniform mixing. The carbonized solidified mixture can be obtained by fully mixing.

[0061] (4) The carbonized solidified soil mixture is crushed and screened through a screening bucket. The material particle size is no more than 15 mm. It is spread on the site after the surface is cleared. After spreading and leveling, it is rolled with a 20t roller to obtain qualified road materials. It has been determined that the optimal moisture content of the road mixture is 17.6% and the maximum dry density is 1.78g / cm 3 The on-site compaction degree is 96.1%. The on-site mixture is formed according to the "Testing Procedures for Stabilized Materials of Inorganic Binders for Highway Engineering". After curing, the unconfined compressive strength after 7 days is 4.7Mpa, the water stability coefficient is 86%, and the antifreeze index is 81%. The carbonized solidified soil road material can be used for filling the subbase of the main road.

[0062] The steel slag powder used in the above embodiments is converter steel slag, in which the calcium oxide content is more than 30%, and its particle size range is 0.075 mm - 2.0 mm; the effective calcium oxide content in quicklime is more than 70%, and the particle diameter is not less than 0.1 mm; the power plant dewatered ash is a by-product produced by the wet flue gas desulfurization process, and its main components are calcium sulfate dihydrate, calcium sulfite, calcium hydroxide and calcium oxide, and the particle diameter is not less than 74 μm; the high-calcium fly ash is an industrial by-product produced by the power plant, the calcium oxide content is not less than 10%, and the particle diameter is not less than 74 μm; the effective component of active magnesium oxide is not less than 80%, the activity index is 40 - 80%, and the loss on ignition is not more than 10%. In addition, in the above embodiments, the ultrafine powder admixture is prepared from stone powder, slag powder, tailing powder, cement clinker and activator according to the ratio of 32:31:15:22:6. However, the ultrafine powder admixture is not limited to the above formula, as long as the specific surface area is not less than 400 m 2 / kg and the activity index dosage is 75 - 95%.

[0063] The specific application field of the present invention is only the preferred embodiment of the present invention, but the application scope of the present invention is not limited thereto. The above embodiments are only to illustrate the technical idea and characteristics of the present invention, and the content described is only the preferred embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Within the technical scope disclosed by the present invention, equivalent changes or improvements made according to the technical solution and inventive concept of the present invention should all be covered within the protection scope of the present invention.

Claims

1. A method for resource utilization of highly water-containing silt-like engineering muck, characterized in that, it includes the following steps: S1. Add a curing agent to the highly water-containing silt-like engineering muck for mixing and dehydration treatment, and then perform crushing, impurity removal and screening to obtain semi-finished muck; the curing agent includes steel slag powder, quicklime, active magnesium oxide and cement clinker, and their dosages are 1-10%, 1-6%, 0.5-1% and 1-10% of the mass of the highly water-containing silt-like engineering muck respectively. The curing agent also includes power plant desulfurization ash or high-calcium fly ash, where the dosage of power plant desulfurization ash is 1-3% of the mass of the highly water-containing silt-like engineering muck, and the dosage of high-calcium fly ash is 1-7% of the mass of the highly water-containing silt-like engineering muck; S2. Put the semi-finished muck into a carbonization chamber for carbonization curing, with the curing humidity of 60-70%, the carbon dioxide pressure of 100-300 Kpa, the carbon dioxide volume concentration of 80-90%, and the carbonization time of 3-6 h to obtain carbonized soil mixture; S3. Mix the carbonized soil mixture with cement, admixture, aggregate and sodium bicarbonate according to the mass ratio of 100:1-3:0.5-2:1-5:0.1-0.8, and supplement water as needed to the optimal moisture content to obtain carbonized and solidified soil mixture; S4. Crush and screen the carbonized and solidified soil mixture, and then perform paving and rolling to obtain a high-performance base material.

2. The method according to claim 1, characterized in that: the highly water-containing silt-like engineering muck is in a plastic state, with a moisture content of 50%-60%, an organic matter content of 5%-10%, and more than 10% of the particles with a particle size greater than 50 mm.

3. The method according to claim 1, characterized in that: S1 specifically includes the following steps: a. Dehydration treatment: Stir the highly water-containing silt-like engineering muck and the curing agent evenly through a powerful stirring head device, and turn it over by an excavator for natural curing to reduce the moisture content of the muck to less than 20%; b. Crushing and impurity removal treatment: Crush and screen the dehydrated muck through a screening bucket, take the particles with a particle size of less than 50 mm, and remove the part with a particle size of more than 50 mm as impurities; c. Screening treatment: Screen the muck after impurity removal again through a crushing and screening bucket device to obtain semi-finished muck with a particle size less than 15 mm.

4. The method according to claim 1, characterized in that: the aggregate is construction waste, with a particle size less than 15 mm, and the content of particles less than 10 mm ≥ 75%.

5. The method according to claim 1, characterized in that: after screening by a crushing and screening bucket in S4, the particle size of the mixture ≤ 15 mm.

6. A road base material prepared by using the method according to any one of claims 1-5.

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